If you're looking for manga similar to 13, you might like these titles.
Fumio is a woman scorned. She’s alienated from her dear friend Kaoruko, but more importantly the love of her life, Takumi, appears to have fallen for a new transfer student at school. Upset and realizing that she can’t live without him, she does the only logical thing: she gets her chainsaw, builds up her resolve, and goes to kill both him and herself...
1 vote
Lead girl, check. School setting, check. Interesting weapons of choice for a school setting, check. Both are hilariouly entertaining shorts that will make you turn the page so fast to see what happens next. Revenge is always an interesting thing in Japan.
The mysterious island Kakuremi Island where the "mimic" live. Watari, a boy who happened to flow into the Kakuremi Island, meets a girl named Mikuri there. Watari who accidentally landed on the island and deepened friendship with the residents of the island. At that time, a crisis comes to the mimic "Noppe".