Zipman!!

Zipman!! (ジップマン!!, Jippuman!!) is a Japanese manga series written and illustrated by Yuusaku Shibata.

Plot
World-famous handsome mechanical engineer Koshiro Tatara and scary-looking musclehead Kaname, these polar opposite twins both fell in love with the same girl's smile. Since then, they compete daily to see which of them can make her smile more. But one day, tragedy suddenly strikes Koshiro...