He's not against it, and Momo has some ideas!

(Gender bending content from here in out.)

"...I guess it would be hypocritical of me to say no to that," Denki said slowly. "Though we're going to have to be honest with him, whoever he is, if we go into that..."

"Oh! Oh, Master, I have an idea!" Momo piped up, raising her hand.

"...this is either going to be too much, or a great, sexy idea, isn't it?" Kyoka mused, looking at Momo flatly. "There is no in between with you..."

"...well, let's hear her out..." Denki mused. "Can't hurt to do that much..."

"Make him a hot girl, and bring her into the harem!" Momo replied excitedly. All three of them would have had spit takes had they been drinking anything at that moment.

"I'm... Sorry, what?" Mina asked.

"Well, you know with my magic, I can make it feel good enough that anyone I affect will consider it worth it~!" Momo reminded Denki. "Sex Genie influence is addictive like that, very few people aren't hooked on it, plus, a little removal of inhibitions and arbitrary sexual taboos from the mind and all that... And he can still access the boy form for time with Mina if you want... Really, there's no limit to the ways we could do this!"

"Wouldn't people notice if someone was suddenly a girl?" Denki asked her. "Unless your magic can ensure that everyone thinks he always was one or something."

"That's certainly one way to do it," Momo agreed. "Or he could just be male in classes or any other situation people would have known him... Or just about any other idea, really," Momo mused. "Then he and Mina could date within the harem!"

"...that does sound kind of hot, if a bit ****..." Mina mused. "I kind of like it... So long as you can assure me that he'd be happier that way. Might be tough to swing with him though, he's obsessed with being manly..."

"Meh, a tomboy never hurt anyone," Momo waved her off. "...too much anyway... How about it, Master?"