Sword Art Online - Vol 5 Chapter 5

Every novel has a slag character, the one who decides to abandon the protagonist at his lowest, most helpless point, either because he can’t stand the poor guy’s circumstances or for other reasons. But after the protagonist wins his way in life again, they’re the ones who beg with broken sobs to be taken back.

Still, water once spilled can’t be recovered again.

Yet the unlucky Shen Jiayan has been bound to a Water Recovery* System to do just that.

*water recovery – comes from an idiom that means “spilled water can’t be recovered” (English equivalent: there’s no use crying over spilt milk).

- Description from Novelupdates

Akira Kuromiya is just an average high schooler who gets killed by a robber. He wakes up and is now a chicken!? Even worse he becomes the familiar of a girl who's apparently the heiress of a powerful clan.

That was for a short while though, as he was abandoned and woke up to find out he, now she, is trapped in a deadly magical forest with all sorts creatures trying to kill her.

The world she finds herself is one of magic and monsters like the manga she's been reading. Akira, now Hinotori is trying to live her life as a chicken in another world!

By coincidence, Li Yunmu found a super machine from humanity’s age of darkness. From that point onwards, his ordinary life would never be the same! Aptitude? Innate talent? What are these? Could they be eaten?

I have neither aptitude nor innate skill, but my shadow can level up using hacks. Experience, Ability points, battle prowess… all of them could be hacked. Even while he is asleep or tired, he could still increase his skills.

- Description from Novelupdates

Collapsed without warning, and upon awakening, he found himself back in his childhood.He thought it was a blessing from above, but unexpectedly, tumultuous changes ensued, shrouded in mystery...