Kimi to Warui Koto ga Shitai - Vol. 2 Ch. 8 - Leave it to me!

[MiguelH224]

The older brother sees what the younger brother is doing and trying, but wants to help the younger brother find happiness; indeed, the older brother wants the younger brother and girl to become lovers.

You got it backwards, the villain is the older brother like he stated in Ch2, the popular one is the younger brother, FMC is in love with the older brother