MTL - Great Demon King - Chapter 987 Brotherhood"?

The Special Investigations Unit is a covert organisation that no-one in the city knows about, dedicated to investigating bizarre occurrences beyond the comprehension of the living. The Chief Zhao Yunlan isn’t a simple guy either, being the inheritor of the Guardian Order, he has always been a righteous conformist, excelling between realms of the living and the dead. While investigating a school suicide case, Zhao is attracted to the calm and reserved Professor Shen Wei, but the Professor seems to be rather fickle towards him…

- Description from Novelupdates

Noah was a nobleman. An orphan.Born with an empty constitution, he was pretty much useless…Until he realises the World’s Greatest Secret.The verse they were living in—It was a freakin fantasy novel.And the worst part?He was supposed to be the villain.***“Hehehe— So what? I just have to substitute someone in my place…Yes!”“All I have to do is to hire a Villain.”

One day, a villainess came to the orphanage.“I absolutely can’t stand children!”“How can someone my age have a child? It doesn’t make sense!”“What’s so great about these little creatures that tire you out all day long…”Setting aside her dislike for children…Somehow, after she arrived, the children started gaining weight.“It’s all because of the contract, you know?”That’s what she says.While personally feeding them sweets she made herself.

Sequel of Allison, taking place about 17 years after the original series.