Story summary: MC is a summoner trainee whom wish to be the very best like no one ever was. Unfortunately, her summoning skill sucks big time and was bullied for that.
Then she finally summoned a cute deformed little shark whereas other summoner trainee manage to summon monster girl/guy they flirt with. They laugh while throwing insult at her, teach slap her in the face and try to kick her useless bum out.
Then the passive skill of that little shark kicks in.
Seeing couples going lovey dovey transforms it into a three headed shark-nado-topus that will slaughter every riajuu and romantic couple in a most gruesome manner possible.
Bloodbath happened.
Hence now we have Hachama being stalked by sharknadotopus that will slaughter every riajuu in sight.