Yomikawa Yoru was considered one of the finest operatives Ichigaya has ever produced. However, when a supposedly easy mission goes awry and his partner gets killed, his performance suddenly drops to below satisfactory levels. His superiors decide to send him to Mihama Academy, where their other dog had also been, sent in hopes of fixing their best asset.

Ayase Eli thought that her time as an Idol was over... but when a talented producer suddenly appears during an unexpected reunion of the former μ's members, she is presented another chance to live her dreams. However, certain organizations are after her life due to the long-guarded secret of her family. Meanwhile, a certain spy arrives that holds the key to her safety and identity.

Some wanted to acquire power for the sole purpose of achieving a state of absolute authority. Others long for it to receive a sense of recognition as greatest.. Albeit, those who become Level 5 are slowly engulfed by the City's Darkness. These are the stories of the Lost Generation of Level 5's that were engulfed by that Darkness 20 years before the current generation of Level 5's.