The mc was shy and beta, naive, like the mc from kanokon

story :

i think he was in empty classroom(seems class is over or such), and the found the female lead changing clothes or such, i think it involve panties , because in the manga summary there is word panties or such.

After that the female lead then blackmail him to do her bidding, her personality was sadist, love teasing the mc ,and was the most popular girl in the school, long hair, beautiful , smart ,etc.

sorry that was what i know, it was 2017-2019 manga i think, and recently updated but i forgot the title, it only had 4-5 chapter translated

edit : someone pm-ed and tell me the title already, named was Haite Kudasai, Takamine San