Zarmen, a rising adventurer, decided to retire from the adventure business, and to graduate from his virginity, he decided to spend all the money he had saved since his reincarnation in a luxury brothel.The woman who appeared in front of him was the finest woman he would ever have known. Thanks to her hospitality, Zarmen fully enjoys his first sex, but at that moment, his ears hear a mysterious announcement, "I confirmed my implantation.", "Level up!""Does this mean that the more "seeding" you do, the stronger you get?"An extraordinary implantable foreign world adventure fantasy created by a bottom adventurer who has been at level 1 for many years levels up through sex! 6p5s43
3 Volumes (Ongoing)

The premise could be interesting if he had to actually work for it and charm women (Like a more explicit version of The World God Only Knows), but it turns out there's a whole host of women who already want him from the start of the series, he's just oblivious to it. Heaven forbid we have a harem mc who isn't denser than tungsten, or actually works for their harem in the series.