Going on the Kikkoman thing, here's a very basic outline of the sort of clichéd stuff that would work:

• Have a few short school days. Lectures, hanging out at school or in town, back home with father.
• Have one or more romantic interests you can choose to go after and a rival.
• Drop some hints that one of the friendly characters hides something.
• TRAGEDY. The father gets killed (and gives the secret kikkou technique in is dying moments) or the girl is kidnapped or the school/town is destroyed or all of the above. The friend hiding something and the rival were behind this, and the masked final boss is revealed.
• HOT BLOODED FIGHTING ACTION
• Go after after the enemy lieutenants one by one. Meet the rival a few times. The fight is always interrupted for some reason.
• Get into a terrible predicament. The rival was actually always on your side.
• MORE HOT BLOODED FIGHTING ACTION
• Shocking revelation about the identity of the big boss. Depending on your actions you may or may not be able to fight. The rival may take a hit for you and die.
• Redemption ending / path of the kikkou ending / protector of the universe ending / romantic ending

Just throwing (bad) ideas.