As a hacker of the renowned hacking group "Steppenwolf", Tooru Souma and his partners earn their living by hacking into servers and selling the information they steal.

As the last hacking before disbanding their group, they hacked into a military server, but soon they find this is a setup by the military to lure terrorists, and they were drawn into battle between two factions. At the end, one of Tooru Souma's friends was killed by an unknown Simulacrum, while most of other group members have been arrested. To investigate and avenge his friend's death, Tooru Souma accepted the offer to join the military.

[From Wikipedia]