Gangster hero manga

Gangster Hero summary:

No. 2 (the rudest and stupidest guy), happens to live with an orphan named Jun Je Young (who has the key to find a diamond). The Sencream Gang is looking for this diamond. Meanwhile, Jun Je Young starts to have feeling for No. 2 (the stupid guy). Seeing her growing LOVE for No.2, Lee Woo Yeun (another guy) starts to gain feelings for Jeh Young. At the same time No.2 wonders if what he feels for Jeh Young is LOVE or just another feeling. Where in the world is the diamond?