Because you like Elaine Benes in Seinfeld

Kyoya Ootori is possibly the only person who could reasonably go from VP of a school club to ruling the world. See them in Ouran High School Host Club.

For the sake of science, Kurisu Makise will persevere no matter how deep into the dark secrets of the world she finds herself. See them in Steins;Gate.

With most of the people that Sango loved now gone, the only thing she wants is to kill the demon who destroyed her village. See them in Inuyasha.

Gou Matsuoka offers to help as manager of a swim team, believing that they're the only ones who can help her brother. See them in Free! Iwatobi Swim Club.

Konata Izumi has a live-now, worry-later view of the world. See them in Lucky Star.

He's the great Black Star, and he's come to assassinate you. See them in Soul Eater.