The Boys With Tomorrow to Conquer(1997)

Shounen wa Ashita wo Korosu

1) Shounen wa Asu o Korosu: The main story revolves around two high school boys struggling at rock-bottom, although they don't even realize it. They are exact opposites in more than looks: Sakuraba is an honor student with an icy exterior, and Fujieda is a hot-headed trouble-maker.

They love to hate, as the saying goes, but as we follow the story through Fujieda's mind we see what may be roiling just beneath the surface. They become tied together when their siblings marry, and side by side they protect each other from gangs and the future.

There are two extra stories in the second volume:

2) Kan no Naka no Watashi no Kedamono is a psychological story taking place inside the tight security of a yakuza base.

3) Indigo Blue: Koga and Shiba don't quite fit into the ordered Japanese system, and so they leave the country. We pick them up again 4 years later in Mexico City. One final dirty job, and they'll have enough to retire to that Caribbean island with the sky of indigo blue...

(Source: Translated Treasures)