Nigasanai yo? Fukuroji-kun

Fukuroji, a high school boy who spends his days trying not to stand out, is forced one day to confess his feelings to the class idol as part of a punishment game. However, he accidentally confesses to Tsubaki Sakura, the school's most feared and fierce-looking girl. In an attempt to clear up the misunderstanding, Fukuroji tries to explain things to Tsubaki alone, but she suddenly takes off her school uniform...!?

(Source: Kadokawa, translated)