Kiss kara Hajimaru Valkyria

Kiss kara Hajimaru Valkyria (キスから始まる戦機乙女〈ヴァルキュリア) is a light novel series by Souhei Tsukimi with illustrations by Yuugen.

Plot
Kiss x Pretty Girl = Valkyrie? For the sake of researching a human's 7th sense "Destruct Sense," I, Shindo Ichirou, enrolled in the newly opened school Epitaph. However, on the first day after school, I was attacked by a mysterious sword, and at a level that which could cut open the skies! At that moment, without understanding what was going on I was painfully saved.

The pretty girl wielding a rocket launcher, Rikudou Mari, said to me: "If you want to keep living, conjure up a Valkyrie!"

Armed battle fantasy beginning with a kiss, start!