[Avrorrange]

Spoiler for brief summaries:

Volume two is about Kamito and co. fighting against the other 'male spirit contractor' who is able to 'use' 72 spirits, as well as the introduction of Fianna and the conclusion of her problems.

Volume three is about Ellis and Rinslet joining the team, as well as the fight against Ellis' sister.

Volume four is about Kamito's past ,the introduction of the teams and fighting against Kamito's osananajimi.

Volume five is about breaking the cursed gear forcibly set on Kamito by the impostor, the initiation of the tournament, convincing Est to fight for him and fighting against Leonora's team.

Volume six is about what the heck happened between Restia and himself in the past, the alliance with Milla's team and the fight against Restia and the 'conciousness of Ren Ashdoll', a.k.a the 'Successor of the Maou'.