Guest and No. 4 have known each other for a long time. Back when Guest was taller than him, No. 4 was a fragile child with thin bones, a small frame, and large eyes.

Guest accepted and raised the No. 4 of that time. No. 4 only allowed Guest to see his faint smiles and engage in physical contact like holding hands.

And around the time No. 4 turned 10—

No. 4 went missing.

Guest searched for No. 4 desperately, but only the hollow sound of the wind returned...

Guest spent nights crying until, eventually, the memory of No. 4 began to fade.