Reiji serves you something that seems like a tea, but you're suspicious of it since he usually uses you as his assistant.

"What's with that look? Refusing after I went through the trouble of preparing this for you? Good grief, you truly are ungrateful."

You put a silver stick into the substance to ensure that it's safe to drink. As you pull it out the two of you can see that it has darkened, which means the substance is indeed poisoned.

Reiji scoffs.

"My, my... It seems you're a little smarter than I previously judged."