Mutsuki confesses his feelings for Kaneki to him and gushes to him while holding his hands how much he loves and adores him and how attractive he finds Kaneki no matter how Kaneki/Kaneki’s body changes due to his life’s trying circumstances/traumas. Kaneki is touched when he learns about the depth of Mutsuki’s feelings for him and how he’ll never betray or abandon him. This is before he leaves the CCG and it’s this scenario that convinces Kaneki to stay with the Quinx as he feels loved

“I’m headed to Rushima.” Inside an empty interrogation room, Mutsuki waits for the Black Reaper to acknowledge his presence. He shakes from head-to-toe. Don’t you love us anymore?

“Good luck,” says Sasaki dully. He meets Mutsuki’s eyes for a second before glancing away.

“Your hair looks good black. And the glasses suit you!” Mutsuki forces a smile. It’s true. It’s just this angry personality that doesn’t fit.

“Thanks.”

“You’d look attractive no matter what, actually,” Mutsuki says with a giggle. He turns to leave, but why? He might die on Rushima. He might never see Sensei again. 

Mutsuki spins around to face Sasaki again. “You know we Quinx love you, right? Even Urie. And I – I adore you no matter what. Even though you’ve abandoned us.” 

He chokes up. “We’ve all been through so much. I can’t – you know we’re a family, right? We’ll never leave you. That’s what families do! Right?”

Sasaki’s face whitens.

“I love you, Sensei. And I want to tell you that. I love you a lot, and you mean so much to me, I promise.” Mutsuki wipes his tears off his cheeks. 

The reaper’s upper lip trembles. Mutsuki loves him? Urie doesn’t blame him? Saiko cares? 

Mutsuki throws himself into Sasaki’s arms. “Please hug me.”

Sasaki obliges. Mutsuki hears him sniffling. “Mucchan, of course I love you all. I’m sorry I’ve been horrible.”

“It’s okay; we’re all horrible,” Mutsuki insists. “Please come back to us. We’re here for you. Always. No matter what.”

Sasaki clutches Mutsuki tighter. For a moment, Kaneki Ken feels loved and safe again, even in is broken family. “Thank you.” 

This is all he’s ever wanted.