MTL - What Should I Do If I Attack the Protagonist Through a Book? - Chapter 29

High-school student Koremitsu Akagi finds himself attending the funeral of Hikaru Mikado, who had died in an accident during Golden Week. He’s not sure why he’s there, as he only exchanged a few words with Hikaru at school. However, Hikaru doesn’t seem to be completely gone from the world, as he comes back as a ghost in order to fulfill a promise to Aoi Saotome, his fiancée. Since Koremitsu is the only one who can see him, he asks him to carry out his promise in his place.

Complying with his request, Koremitsu tries to fulfill Hikaru’s promises to the rest of his “girlfriends”, helping them overcome past misunderstandings and repair broken relationships.

When I was reborn in South Korea, I wanted to live my life in peace. Pass the activation system, unlock the 'Big Brother' career, obtain the invincible system, and embark on the road to power

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

This is a story about the protagonist getting the system, going crazy in the biochemical apocalypse, producing aircraft and tanks, destroying zombies, saving good people and killing bad people.

- Description from novelbuddy