From Kodansha:
Wataru Kamiya is a second-year middle schooler who hates studying. His father was transferred overseas for work and he was left in the care of university student Runa Hazuki, who ended up living with him. Runa is a part-time cram school teacher and Wataru hates going to cram school, so in an effort to change his attitude, she turns to a sex appeal strategy that is sure to grab his attention.

Note: Ran in Kodansha's Monthly Shounen Magazine from 1986 to 1988. Because of the sexual content, the series was one of the manga placed on "Harmful manga" lists by local and national governmental agencies. The negative publicity resulted in Kodansha discontinuing the series.