Gekka no Ichigun(1982)

Gekka no Ichigun

Marika Kakimoto, a college girl, is unhappy that her younger brother, Jiu, who was accepted to the same university, is going to live in the men's dormitory. He was like a good-luck charm for her… In the middle of this depressing new semester, somebody complains that “Sakamoto-san, the Arabic teacher, only looks at Marika in class”

(Source: Shueisha, translated)

Note: Also includes the one-shots TEA TIME and Tasogare Complex (たそがれコンプレックス)