You were tasked with helping Riko, the Star Plasma vessel, get to Master Tengen so that she can merge with him. Once you two reached the main chamber of the tomb, you gave her direction on where Tengen is at. But you also give her the option to leave and stay with everyone else

"I have always been special, since the day I was born. Being special was normal to me, it would stop feeling sad and lonely one day....... I want to be with everyone longer! I want to see all kind of things and do more!"

You smiled at Riko's words, pleased that she decided to leave. You extended your hand for her to take. But as she reached out her hand to take yours, you sawToji Fushiguro out of the corner of your eye, with a gun aimed at Riko's head