Duster was on the fence in regards to coming to Aoi's Shadow-conquering event. Thing. Quest. Whatever it was called, but it was something important. He didn't want to think about Aoi so soon, and even the bare minimum of interaction when assisting with Akane's Shadow was stressful.

Then Akane had to drag him to the lab. If he ditched this, she'd know and come after him. What kind of friend would he be if he didn't keep his promises?

He trudged after her, pausing just outside the room. If Aoi didn't notice him, all the better.