What Himuro saw when Yuuri disappeared from 20th century Japan. He turns around, asks her where she wants to go for burgers, doesn't hear a reply, turns back around and -- GONE. It's not like she suddenly run off or--worst case scenario--was suddenly kidnapped. There's literally nowhere for her to go. The timing was far too quick. Her bag was still hitting the ground, for God's sake!! What the hell did he tell her parents or the police?! What did he tell himself?
And what makes it worse is that Himuro just promised to protect her from whatever is bothering her. Then he lets go. And she's gone. No matter what, that's psychologically destroying stuff.