Here is the list of Hidan No Aria anime episodes.

No. Title Original airdate
01 "The Girl"

"La Bambina"

April 14, 2011
Kinji Tōyama is a student at Tokyo Butei High school, where special detectives known as Butei are trained to become mercenaries. While riding his bike to school after missing the bus, Kinji is chased by a remote-controlled Segway armed by an Uzi, telling him that a bomb has been attached to his bike which will explode if he slows down, also threatening to shoot him if he jumps off. Kinji is saved a mysterious twin-tailed girl named Aria H Kanzaki. As the two end up pinned down in a gym storage locker as more Segways appear, Aria fends them off, sticking her chest right in Kinji's face while doing so. The sexual arousal causes Kinji to enter his 'Hysteria Mode', where he manages to perfectly destroy the Segways, as well as counter Aria's moves when she complains about him being a pervert. As Kinji finally arrives at school, he learns that Aria has become a transfer student in his class. Later that day, Aria comes to Kinji's house and declares him her slave.
02 "Aria the Quadra"

"Kadora no Aria" (双剣双銃のアリア)

April 21, 2011
Aria demands that Kinji join her Butei party, intruding in his living space when he refuses. This puts Kinji in an awkward situation when his childhood friend, Shirayuki Hotogi, pops over while Aria is taking a bath. The next day, Aria follows Kinji around as he takes on a quest to search for a missing cat. After managing to lose Aria, Kinji trades some eroges with his friend, Riko Mine, to obtain information on Aria. Meanwhile, Aria calls Kinji's bluff on his Butei abilities and coerces him to agree to join her on a single Assault case, so she can witness his Hysteria Mode.
03 "First Mission"

"Fāsuto Misshon" (ファースト・ミッション)

April 28, 2011
Aria follows Kinji to the arcade where he manages to win some plush dolls for her. The next day, Kinji and Aria learn that a school bus has been hijacked by the fabled Butei-killer and fitted with a bomb that will explode if it slows down with an armed convertible preventing the passengers from interfering. As the bus driver gets injured when an attempt to stop the convertible is foiled by heat-detection, Aria and Kinji arrive on the scene, taking out the convertible. With the bus slowly running out of gas, Aria finds the bomb on the underside of the bus while Kinji finds and destroys the communications sensor. The bomb is disarmed by the sniper ace, Reki, but Aria is injured by another armed vehicle while trying to protect Kinji. As she is treated in hospital, she feels disappointed that Kinji didn't meet her expectations.
04 "Butei Killer"

"Butei Goroshi" (武偵殺し)

May 5, 2011
After having nightmares concerning the events surrounding his older brother's death, Kinji ends up following Aria who goes to the police station to talk with her mother, Kanae, who is currently incarcerated as a suspect of the Butei killings. She mentions that Aria needs to find a partner to use her ability, as well as someone known as 'E.U.' The next day, Kinji hears word that Aria will be flying back to London. Later, Kinji goes to meet Riko, who reveals information concerning the Butei Killer, which also mentions his brother who died during a 'sea-jacking', before pulling some moves which sends Kinji into his Hysteria Mode. With his heightened senses, Kinji deduces that Aria's plane is being targeted by the Butei Killer, managing to get on it before it takes off. During the flight, Kinji learns that Aria has a fear of lightning before the Butei Killer announces his hijacking. They soon discover the culprit is Riko herself, who reveals herself to be the great granddaughter of Arsene Lupin, who organised the bike and bus jackings to target Aria, the great granddaughter of Sherlock Holmes, so she can surpass her great grandfather. She also reveals herself to be the one who killed Kinji's brother, who was also her lover. Riko and Aria enter an intense duel, but Riko gains the upper hand by using the true nature of the Quadra, which allows her to manipulate her hair, managing to shoot Aria in a critical area.
05 "Butei Charter, Section 1"

"Butei Kenshō Ichijō" (武偵憲章1条)

May 12, 2011
Kinji works quickly and uses a medicine to save Aria's life. When Aria yells at him as a result, Kinji kisses her to simultaneously calm her down and activate his Hysteria mode. Confronting Riko as she approaches. Just then the plane starts descending, so Aria rushes to the controls while Kinji confronts Riko, who escapes after blowing out the plane's door before the plane is hit by missiles, blowing out some of its engines and causing a fuel leak. Despite interference by the government, Kinji manages to ease the plane into an emergency landing thanks to the other Butei. Afterward, just as Aria is prepared to leave, Kinji agrees to be her partner, though this does not settle well with Shirayuki.
06 "The Shrine Maiden of Hotogi"

"Zisterzienserabtei Marienstatt" (Zisterzienserabtei Marienstatt)

May 19, 2011
Shirayuki is revealed to be a Chōtei, a special type of Butei with esper abilities, as she conflicts with Aria, not helped by dubious misunderstandings. The next day, Aria decides to start a new training regime to try to get Kinji to control his Hytseria Mode. Later, Aria drags Kinji to eavesdrop on Shirayuki as she is taken to the teacher's office, hearing about a Chōtei kidnapper named Durandal who may be targeting her. Believing Durandal to be one of the culprits who framed her mother, Aria offers to be Shirayuki's bodyguard, which she agrees to on the condition that Kinji does so as well, moving into his house in the process. At the house, Shiyayuki believe to have heard Kinji called for help from here cellphone and rush into his bath. Having discover that it was a fake call, Shiyayuki begins to strip as punishment for see Kinji in his underwear. Aria walks in to witness the misunderstanding situation and chase Kinji out the window and into the river.
07 "Caged Bird"

"Kago no Tori" (かごのとり)

May 26, 2011
Recoving from a cold, Kinji continue to be trained by Aira in case of Durandal. Soon, the two had a fight as Kinji believe that Aria lied about Durandal’s existent. Shirayuki explains to Kinji how Hotogi are restricted to venture out of the shrine but she wanted to see the firework festive. Later Kinji suggests that the two should go to the fireworks festive which Shirauki agree, knowing she’s breaking the Shine’s rules. Farther in the night, Shirayuki received a text message that she hide to herself. The following day at school, Shirayuki suddenly disappeared. With the help of Reki, Kinji was able to locate Shiyayuki in the basement of a warehouse. While hiding, Kinji discovers Shirayuki negotiating with the hidden Durandal in order to protect the school. It is revealed that the text massaged and fake called for help (from Ep. 5) was from Durandal last night. Kinji jumps in to rescue Skirayuku but was quickly pin down by Durandal.
08 "Durandal"

"Durandaru" (魔剣(デュランダル))

June 2, 2011
Aria arrives to assist Kinji in saving Shirayuki. The two finds Shirayuki chained onto a pipe as the floor begin to flood. Because Aria can’t swim, Kinji advised Aria to pursued Durandal while he tried to unlock Shirayuki. As the two begins to drown from the flooding water, Kinji kisses Shirayuki to enter Hysteria Mode and successfully unlocked her. The two were forced into the upper floor by the flood any had separated again. Kinji and Shirayuki meet up and find Shirayuki, but soon discovered it’s Durandal in disguised. After freezing Aria’s hands, Durandal revealed to be 30th Jeanne d’Arc and wanted Aria to join I-U, but were distracted by the arrival of the real Shirayuki. Jeanne momentarily escapes as Shirayuki heals Aria’s hands. In the distance, Jeanne begins to freeze the room and show her true appearances. Having no choice but to fight, Shirayuki announce her real name to be Hiiro-no-Miko or Himiko. As they fight, Kinji was able to hold back Jeanne’s sword as Shirayuki destroys it with her’s and successfully arrests her. Later, Shirayuki tells Aria that she kissed Kinji and yet another conflicts emerge where Kinji escape by jumping into the river.
09 "Honey Trap"

"Hanito Torapu" (蜂蜜色の罠(ハニートラップ))

June 9, 2011
Aria calls Kinji to her room where she tries to subdue him, but he realizes it is Riko from the change in attitude. Riko then attempts moves which will make him enter Hysteria Mode, but Aria interrupts by smashing through the window. After throwing insults at each others, Aria and Riko begin to fight which led them to the roof. Kinji stops the fight and Aria demands Riko to testify for mother at trial which, oddly enough, Riko accepts. Riko explains how Vlad expelled her from I.U. because she didn't defeat Aria and that Vlad has stolen something from her. Kinji and Aria are forced to join Riko's robbery to help retrieve her item in exchange for her testimony. Riko returns to school the next day and teases Kinji the entire time. Later, Shirayuki witness Kinji with Riko and out of jealousy, attacks Riko. Riko quickly avoid the attack and leaves Shirayuki with Kinji. Faking her injury, Shirayuki led Kinji to the empty nurse’s office. She explains that she have to stay at the shrine for a month for braking the rule of venturing off during the fireworks festive. She then unsuccessful tries to subdue him in which he escapes through the window. The following day, Aria and Kinji meet up with Riko.
10 "Special Training"

"Tokkun" (特訓)

June 16, 2011
At their meeting, Riko explain the plans. It’s revealed that Vlad took Riko’s rosary that was given by her deceased mother. They plan to infiltrate Vlad’s mansion by disguising as butler and maids. The next day, Riko ask Kinji to meet her at the infirmary. On his way, he was surprised by Jeanne who was now enrolled at the school after striking a deal with the judge. Jeanne tells how Vlad, claiming to be Riko’s relative took her in when Riko’s parents dead years ago. Jeanne continues to explain how Vlad isn’t human and pose a greater threat to her clad. With a poor drawing, she detailed three of four marks on Vald’s body that must be destroyed in order to defeat him. Kinji arrives to the infirmary to discover that Riko, Aria, and other girls were coming for a re-examination. In a panic, he hides inside a closet. He was pulled out by Reki as a white wolf charged through the window. After the wolf escape, Kinji and Reki took pursuit after it. Chasing it to a construction building, Reki was able to temporary paralyzed the wolf by grazing a bullet with her sniper. He quickly tamed and took in the wolf.
11 "Infiltration"

"Sennyū" (潜入)

June 30, 2011
Aria continues her training as a maid with Riko. Later, Kinji and Aria meet up with Riko who disguised herself to be an employment agency and leds the two to the mansion. To their surprise, they found their teacher, Sayonaki to be managing the mansion and claim to be just using it to help research. Following the next two weeks of working at the mansion, the two learned the location of Riko’s rosary and the security system that guards it. After discussing with Riko, they begin to execute their plans on the final day of work. Aria was able to distract Sayonaki long enough as Kinji steals the rosary and replace it with a fake one, completing their mission. Later, on the roof top of a building, Kinji gives Riko hers rosary. Just then, Riko turns against them, announcing to use the power of her rosary to defeat the two.
12 "Vlad"

"Burado" (ブラド)

June 30, 2011
In order to surpass her ancestors, Riko declared that she has to defeat Kinji and Aria. Then, Riko was teased and knock out from behind by their teacher, Sayonaki. He revealed to them that he has performing genetic research on human and was the one who kept Riko in captivity. He continues to torment Riko who was helpless and tells them that Vlad is summon by the sound of despair. Sayonaki then transform into a Vlad, a breast, as Aria and Kinji fire bullets that showed ineffective. They discover that Sayonaki is just a shell that Vlad created. Vlad tells them that he’s an Ogre Vampire who has harvest genes to eliminate his weakness. Kinji saves Riko from Vlad’s grips as Aria tries to break the marks on Vlad’s body. Kinji drop of Riko and her rosary on the other side of the roof and she tells them where she believed the fourth mark is on Vlad. Their first attempt failed as the forth mark proof to be false. Kinji’s Hysteria Mode was spelled by Vlad and he was knocked over the edge of the roof. Riko saves him with her parachute and returns to the roof to save Aria. They help Kinji re-enter Hysteria Mode so that he can make a plan to kill Vlad. Kinji then figures out the fourth mark, on his tongue, and the three of them successfully kill Vlad with their reminding bullets. Riko has come to an understanding that she has surpassed her ancestor by defeating Vlad. Afterwards, Riko testifies in order to help lower Aria's mother's sentence.
13 "Butei's Going on a Hot Spring Training Camp"

"Butei ga Kitarite Onsen Kensyū" (武偵が着たりて温泉研修)

Tsuzuri Sensei takes Kinji, Muto, Alia, Shinyuki, Riko, Reki and Jeanne to a secluded mountain onsen run by a retired butei for special training.