MC is given a boatload of tr*sh skills but these are actually monster or plant skills and so on, like disease and uses this to power level passively everyday. Like turning his saliva into adhesive or basically magic photosynthesis.

The love interests are his biological niece (main heroine).

a young widow who told her 5-8 year old twins to seduce MC saying he's a lolicon while pining for him because he hired her with her kids. Two young orphans, a boy (confessed) and a girl (has potential).

Adventurer guild receptionist who he made a impression on, and the female knight commander because he's cordial and sympathetic to her.

Another is a stalker with super speed cheat (time stop) since middle school because he treated her like a customer (he doesn't recognize her).

There is the trap court wizard Sylvia or Shuri. (Dunno why they name their boy that but is translated as Shrivia). The next trap is the guy with a magic creation cheat that turns himself into a woman, Matsuri.

There is more if you read it. The story has lots of interesting inventions though, like using magic crystals as rechargeable batteries with spells and solar charging instead of disposable ones. Or using the s*upidest and weirdest skill ever, "poor extortion" which is basically making your own leg shake and leveling it up until it can cut a golem boss made out of Oricalcum with it, then turn it into a magic chainsaw enchant.