Omake no Kobayashi-kun

From Impossibility:

This is the story of four high-school students whose family name happens to be Kobayashi that end up in the same class. No Kobayashi is similar to another Kobayashi and in fact, three of them are considered something similar to the Bermuda triangle. Anybody who gets near, ends up... well... that's better left unsaid.

New student Kobayashi Yamato is not afraid however, and already considers them like brothers and sister! Will his naive youthfulness be crushed forever? Will the everlasting power of "always happy attitude" overpower the famous trio? Will anybody survive the year?