Buso Renkin

Kazuki and Tokiko befriend the Hayasaka twins, Shusui and Ouka. However, the twins are actually humans working with the LXE ordered to kill the Alchemist warriors at the school. When two LXE Homunculi invade the school, Kazuki and Tokiko intercept the threats, causing the twins to realize who the Alchemist Warriors are and that they must kill their friends.