Seishun Senshi Asahi-kun

The protagonist, Asahi Mononobe, is a high school freshman who loves the once-popular battle hobby "Battle Pin." He's shy and whenever he talks to people he becomes an awkward "ahe"-ing Asahi... But he really wants to have a "youthful" life!! Suddenly, Asahi and his partner, Red Sun, find themselves caught up in a war that threatens the survival of the Earth from their peaceful everyday lives. Will Asahi be able to have a proper "youthful" life!?

(Source: Shogakukan, translated)