Overall plot of OnS being like:
Guren: "I lied. It never was possible to bring these kids back to life in the first place, Yuu. I WAS ONLY USING YOU!"
Ferid: "My, my, isn't that shocking? Well, since we're at it, I was only using you, too, Guren. To get Saito to notice me again~"
Saito*dangling from the ceiling*: "Isn't that sweet? But unfortunately I have to tell you that I was also just using you to use Guren who would use that kid. And everything just to please our dear first progenitor~"
Shinoa*with demon marks on her face and Shikama Doji's voice*: "And I used both of you and sweet little Mahiru to use Guren so he would use Yuichiro Hyakuya to destroy the world but this time completely. Furthermore I used little Shinoa here as a vessel to observe you using each other."
Kimizuki: "Well, since it's no use hiding it any longer anyway. I only used my squad in order to help my sister."
Yoichi: "I also have to admit that I was only using you guys to hide my dark, twisted personality..."
Narumi: "It was prety much clear from the start anyway already but...I was also only using you to bring my squad back to life."
Krul*still on a burning stick*: "And I was using Mahiru Hiiragi in order to get my hands on Yuichiro and Mikaela to use them afterwards to get my brother back."
Guren: "Okay, enough with that already! Isn't there at least one person in here that wasn't using ANYONE?!"
Guren: "Thank god, at least someone who-"
Mika: "Actually I also only used Krul to get Yuu-Chan back."
Guren: "Are you fucking kidding me?! Wait, what about you, Mitsuba?"
Mitsuba: "What do you expect? I don't have enough screentime to even plan to use anyone."