The Exorcist - Chapter 3Book 7: : Ghostbusters

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates

He was summoned by 3 milfs and 2 gilfs, only to realize he wasn't a typical hero with powerful skills.He was a hero with “gifted semen” which can boost battle power or grant random skills.Since then, there has been a long queue of women outside his inn to receive his “blessing”.Mature woman from east, powerful women from west, nuns from south and naughty milfs from south, they all chant his name from their slutty mouth.In bed, of course, Lol.

…Ring! [ The Unique Skill ‘Grand Devourer’ has been acquired! ]

That’s how it first started.
And then… it didn’t stop:

[ The Unique Skill ‘Evolve’ has been acquired! —
[ The Passive Skill ‘Jelly-like Shapelessness’ has been acquired! —
[ The Passive Skill ‘Resistant Body’ has been acquired! —
[ The Unique Skill ‘Dwell’ has been acquired! —
[ The Unique Skill ‘Skill Copy’ has been acquired! —
[ The Passive Skill ‘Mana Perception’ has been acquired! ]

Up until…

[ The Passive Skill ‘Consciousness’ has been acquired! ]

And then I was through—

Normally, monster-type creatures don’t just pop up in some random place—let alone a human place—out of the blue, and without notice.
Yes, if we’re talking ‘normally’, monsters belong more to places like remote, hostile grounds: they ought to be from dark, nasty forests, old caves, or abandoned, ancient ruins.
As I said, it was only so long as we spoke of the usual deal, however. For better or worse, I wasn’t your regular mob.
So, forget about all the remote, uneasy places humans hardly go to—all the abandoned forests, caves, or dungeons I, a monster, should have been from—and picture a bright, lively family restaurant, in an oh-so-peaceful human village. A restaurant where people ate, chatted, and jested together, all having a good time, blissfully oblivious to the fact that, very soon, I would be cutting them all down.

By magic, a monster-type creature spawned in such a place. It was me.
So far, for the few seconds I had been living, it was quite the good life… I got to listen to a fantastic story being told and shared a cool moment with people.
However! Following an uncertain course of events, I happened to be put up against a wall, with a sword aimed at my chest, before I was mercilessly killed.

I, a unique monster, just spawned in that restaurant, with no clue regarding what was going on.
All I knew was that I wanted to live and survive.
Also, I knew I wasn’t your regular kind of monster.
Thankfully, I’d been granted unique abilities before I showed up.
That is how I managed to survive.

In his last life, he was a superstar that dominated the entertainment circle. In this life, he is a rebellious second generation wastrel.