I don't exactly remembered when but I think I last read this manga within this year.

The uke(cute type?) went to a massage place(?) then somehow was aroused. Seme is the masseur there. They did the deed there.

I barely remembered that the uke has a brother that he introduced the seme as his lover (?).

The only one I can think of is Koisuru Hypnotic Therapy but I'm not entirely sure if it fits the second part of the description (´・ω・) It does fit the first part tho (´・ω・)

ive got a disease called having a big brain and excellent taste.

I rarely update my lists by this point.

[img]https://www.mangaupdates.com/image/i284445.jpg[/img]
Ore no ××× ga Genki ga nai Ken Nitsuite
by ko
?

This is it!

Thank you for the efforts 😁