Angel Beats!

Otonashi awakens in a school with no memory and encounters the sniper rifle carrying girl Yuri, who informs him that he has died and is in heaven. Yuri then proceeds in trying to recruit him into her armed struggle against God and the student council president / Angel named Tenshi.

Yuri decides to descend to the Guild for the day to see the situation of the Guild(the guild makes supplies like guns and ammunition). While going down they see Noda who has not seen Otonashi as a companion yet. As he was about to try to kill him 1000 times(in episode 1 he kills Otonashi 100 times) the trap gets set off and Noda gets smashed to the wall. They find out that because the Angel found the place that they reactivated the traps. They fight their way to the guild(Ooyama keeps on forgetting all the traps). Takamatsu gets run over by a steel ball, Matsushita gets cut to pieces by lasers, TK gets squished by the ceiling while saving the others, Ooyama falls as the floor collapses, Hinata falls also because of groping Yuri on accident while climbing(a human ladder)(on the butt or chest (don't know)) and gets kicked and falls down also, Fujimaki drowns because he cant swim, Shiina falls down a waterfall after trying to save a cute toy dog(she doesn't realize after seeing it close(Shiina's weakness is cute things)). Yuri and Otonashi are the only ones left. While drying themselves up Yuri tells her tragic life before coming to the afterlife. They arrive at the Guild and decide to blow the place up and go to the old guild(you can make anything as long as its nonliving using your memories even out of dirt). While Yuri buys some time for them to get ready to blow the place up Otonashi saves Yuri from getting stabbed in the head by Angel. They blow the place up and Angel falls down in the explosions. They go to the old Guild and Yuri calls the others to come to the old guild quickly before Angel recovers. In the end Otonashi praises Yuri of being a great leader.

Yuri decides to have Girls Dead Monster distract Angel long enough to sneak into her room and crack the password on her computer, but Yuri does not think the new ballad called "My Song" the band's vocalist and guitarist Iwasawa wrote would be useful for the operation. While taking a break from shooting practice, Otonashi hears Girls Dead Monster playing and talks with Iwasawa while the band is taking a break. Iwasawa tells Otonashi how her parents used to always fight and music was her only escape. After she graduated high school and left home, Iwasawa began to follow her dream of making music and soon showed promise. Unknown to her, an old head injury caused during her parents fighting developed into a stroke and subsequently her death. When Yuri's operation begins, Girls Dead Monster starts playing in the auditorium while the others, with the aide of the hacker Takeyama (who likes to be referred to by his username "Christ"), break into Angel's room and hack her computer. Girls Dead Monster are soon subdued by several teachers, but Iwasawa breaks free and begins playing "My Song", but disappears after she is finished. This indicates that one does not necessarily have to obey Angel in order to disappear. The SSS learn that Angel is not getting her powers from God but is making them herself, the same way that the team is creating weapons.

With the lead singer of Gldemo now obliterated, a replacement must be found. The manic, high-strung Yui tries desperately to assume the role. Hinata, meanwhile, seeks to avenge a mistake made long ago on the baseball field by assembling the strongest team possible to defeat the other teams in the school. Otonashi worries the game could strike Hinata out in more ways than one. Source: crunchyroll

To strip Angel of her scholastic power, Yui devises a plan for the Battlefront to replace Angel’s test results with bogus ones. She will be shamed, stripped of her title of Student Body President, and be out of their way for good. But they never realize the one who replaces her may be even more sinister than Angel could ever be. Source: crunchyroll

When Angel is believed to be breaking scholastic code, Naoi uses this infringement to exert his growing power and places both Angel and Otonashi in a prison within the school. They discover that Naoi is using his power in violently, and Angel and Otonashi must escape or risk heavy casualties. Source: crunchyroll

Now that Naoi has seemingly joined Battlefront, Yui persuades Otonashi to let his powers of hypnosis help him recover his memories. But Otonashi may not be ready to remember such a tragic, painful past. But there are other issues at hand for the group—such as banding together to capture the mysterious creature from a nearby river known only as the Monster Stream. Source: crunchyroll

With Otonashi's and Angel’s newly formed alliance, dark and powerful clones of Angel have begun attacking the Battlefront with greater aggression. They must return to the trap-rigged Guild once more and risk heartbreaking, violent losses. Source: crunchyroll

With the Angel clone situation becoming uncontrollable, Naoi proposes that they once again call upon the genius hacker, Christ. Meanwhile, Otonashi begins to remember his past. Source: crunchyroll

Otonashi decides that the high-strung singer, Yui, needs to be pushed into finding peace and “moving on." To do so, he enlists Angel who shows him her new weapon: the dark and evil-looking Hand Sonic 5. But Yui has other plans—namely to beat the boys of Battlefront in a violent game on the soccer field. Source: crunchyroll

As Hinata and Otonashi talk with Naoi, something strange happens: his shadow takes an enormous, evil form and engulf him. Weapons are powerless to stop the creature. Making matters worse, the Shadow monsters are multiplying and taking control of the members of Battlefront and the NPCs. Source: crunchyroll

The Shadow monsters show no signs of stopping as more Battlefront members and NPCs fall victim to their strange, marauding power. Yuri takes a dangerous trip into the darkened Guild. In her search to find out just who—or what—is behind these new events, she discovers even darker secrets about herself. Source: crunchyroll

When she awakens from her dangerous solo mission, Yuri finds her surviving friends in Battlefront seem to have found peace. In an impromptu “graduation” ceremony, they all take steps to move on to the next level of existence. But this transition seems most difficult for Otonashi, as it means losing his newly formed bond with Angel. Source: crunchyroll