Kiznaiver

One day, Naho Takamiya receives a letter written to herself from ten years in the future. As Naho reads on, the letter recites the exact events of the day, including the transfer of a new student into her class named Kakeru Naruse. The Naho from ten years later repeatedly states that she has many regrets, and she wants to fix these by making sure the Naho from the past can make the right decisions—especially regarding Kakeru. What's more shocking is that she discovers that ten years later, Kakeru will no longer be with them. Future Naho asks her to watch over him closely.

At the turn of the century, the Angels returned to Earth, seeking to wipe out humanity in an apocalyptic fury. Devastated, mankind's last remnants moved underground to wait for the day when the Angels would come back to finish the job. Fifteen years later, that day has come... but this time, humanity is ready to fight back with terrifying bio-mechanical weapons known as the Evangelions. Watch as Shinji, Rei, Asuka and the rest of the mysterious shadow agency Nerv battle to save earth from total annihilation.

A Happy alien, Takopi, lands on Earth with one mission: to spread happiness! When he meets Shizuka, a lonely fourth grader, he vows to bring back her smile using his magical Happy Gadgets. But as he uncovers the pain in her life, Takopi learns that true happiness may require more than gadgets.

A supernatural system allows people to take revenge by having other people sent to Hell via the services of a mysterious entity and her assistants who implement this system. Revenge, injustice, hatred, and the nature of human emotions are common themes throughout the series.