Nanami's "Six-Two-Three"

Makoto Harada, a bullied boy who likes fighting games, happens to become privy to a secret about the student council president, Nanami Fujisaki. Makoto threatens Nanami until she promises to participate in a fighting game tournament, but she is a complete noob!! Makoto teaches Nanami the inner mysteries of fighting games...!?

(Source: Shogakukan, translated)