Izumi has that problem where he has trouble resisting Mizutani's pout, so when faced with it, he tends to go back to the baseline of his argument. In the present case, said argument is "Hell no."
"But you said if I got more RBI than you in a game, then..."
He did say that, although in a 'when pigs fly' kind of way. He can only suspect that Momokan either heard him or takes the whole give-everyone-a-chance-to-shine thing way too far, because five days later she placed Izumi third in the batting line, followed by Tajima, Hanai, and Mizutani.
It's safe to say that he's never been so horrified to see a teammate hit a triple with all bases loaded, nor ever so pissed at Abe as when he added insult to injury by getting Mizutani home. "I meant an official game."
"You didn't mention that."
Note to self: get Abe to stop imprinting his logic and observation skills on Mizutani, no good is coming out of that. He sighs. He enjoys Mizutani's presence in a variety of circumstances and positions, but the fact is that the guy gets clumsy at the worst possible time and letting him be on top is not an idea Izumi's entirely comfortable with. But he did promise. "Right. Okay. Where?"
"Huh, don't you usually..."
Usually, Izumi has a knowledge of his parents' timetables that is less that of a devoted son and more of a stalker. But there is no way he's letting this happen in his house. Mizutani wants this, fine. He can work for it.
Izumi did, after all.
"But we've always gone to your place!"
"Because I wanted you to not have to worry about anything. Now it's your turn to take care of the logistics." It seems to work, at least enough for Mizutani to frown even deeper and head for his classroom without a further word.
Which forces Izumi to ask Shinooka to pass him a message along when she gets to class. She blinks a little but doesn't ask when Izumi says he'll understand, and repeats dutifully. "'Don't forget the supplies,' right. I'll tell him."
The next week is spent on tenterhooks, but the topic isn't brought up again.
A second week goes by. Izumi kind of forgets about the whole thing.
On the Sunday of the third week, Izumi finds himself trussed up in the pirate-themed room of a love hotel. And really, horribly, he only has himself to blame.