Break-Age

The plot revolves around an intranet-based online game, D.P. (Danger Planet), which is played using a V.P. (Virtual Puppet). VP is literally an avatar which a person uses in the game. However, unlike avatars (characters) from current online games, a VP is allowed to be modified (modded) by a person if he or she has sufficient programming skills.

Kirio Nimura, a normal high schooler who likes games. He and his friend Kurata always plays Danger Planet after school, one day they meet a very tough opponent.

(Source: MU)

Included one-shots:
Volume 5: Last Stop, Yuusha Isetsu