Ara Waga Tono!(1973)

Ara Waga Tono!

A slapstick romantic comedy featuring the hijinks and romance of Japan's first co-ed high school.

Subtitled in its Hakusensha reprint as 'Another Mari and Shingo', as the leads originate as supporting characters in this work.
(Source: The Rose Garden)

Note: Contains the one-shot Shindemo ii (死んでもいい) in volume 2