Oji-san to Marshmallow - Vol. 1 Ch. 3

[MangaDex]

 

[magusix]

FFS! I need more than this god DAMMIT! The anime wasn't enough and this is too little! ffffaaaaaAAAAAAACCCKKKKK

 

[UncleBenny]

@magusix wait, what anime?

 

[Perim]

@UncleBenny https://myanimelist.net/anime/31848/Ojisan_to_Marshmallow
It's a Pixiv series (which ended at ~175 chapters). There's also an after story (which ended after ~19 chapters).