The story is called Usagi drop, I believe.
But the Mc is 30 lol
Nooooo but thank you i remember the little girl was like a toddler she also had red hair she was so adorable i dont remember how old the dude was but i remember him being a potential college student
Good luck finding the story though. I don't know any names of ones that follow your description, sadly
Its okay thank you
I found it its called Baby, kokoro no mama ni
Oo glad you found it
I think hes a college student and her ends up taking care of a little girl they aren't related i think they ended up bumping into each other a lot and eventually he started taking care of her occasionally with the parents permission i think she has red hair and i remember this scene where they encountered each other in a park and the little girl likes collecting rocks and she collected too many and it made her pants fall
Also hes been in love with this girl for a very long time i think and he also trys to get with her and she seems into him