Penguin☆Brothers

Hina's new high school is strange to say the least. She moves back to her old home town only to find that the high school is run by two opposing factors, and students identify themselves based on the color of their school uniforms: Black for the followers of the loud, violent Nishizaki, and white for the followers of quiet, clean-freak Isshiki. And then there are the "grays," who wear street clothes. Hina finds herself stuck between the leaders of the two factions, and it seems to be turning violent.

As one might guess from the girly art and the Ribon publisher, the plot develops a romance element pretty early on in the series. There's a love triangle involved among two of the group leaders. Who will Hina choose?

(Source: MangaDownloads)