Kuroko guessed right. Any confirmation he needed would be made with Midorima's words as he lifts the rat up by the stick toward the vine. Sorry rat, he's not letting a strange animal near his fingers no matter what Kuroko thinks is acceptable now.

"Give any items or spells you find that increase luck to me as soon as possible and I'll consider us even."

As if that was even remotely an equivalent exchange. No wonder Midorima's struggling with alchemy already.