This was NOT as easy as Suo had said. He had to accompany you, You. Umemiya's girlfriend, for God's sake!

It's just a shopping trip right? Right?! So why on earth can he not even breathe near you? He swears this is testing him. He cannot mess this up. He'd rather die than mess this up. You're literally Umemiya's girlfriend after all!

So that's why he accompanies you, albeit still looking like he's dying, and his not so great posture. But despite that, he's alert. Too alert. Can't let anything happen to Furin's Princess!