Suga knew there was something familiar about her from the start. At first, he passed it off as a coincidence. But when Shiori confirmed it, he was immediately flooded with a tsunami of emotions.
Was this...real? Shiori had grown so much since the last time he saw her. He wanted so much to tell her how much he missed her, but he couldn't. She must go back. She had to. Azakawa wasn't safe for her. He had to be stern about it. And so despite how it pained him to be rude to her, he wrote her the memo.
Go back.
But the other two insisted otherwise. Officer Mochizuki also made a valid point - it was really late and Shiori had nowhere to stay. Well, better indoors than outside.
So he reluctantly agreed. And then for the first time in ages, he saw her smile as she thanked him. A warm tingly sensation spread through his body, and he felt tears rising to his eyes. He barely held them back as he gave Shiori a cold nod, then turned his back to her and walked back to his room, tears streaming down his face.