Looks like Megumi hadn’t given up in her pursuit after all. She just changed her tactics from trying to get Yamato to fall in love with her to slowly pulling anyone who is close to Mei.
Megumi lied to Yamato telling him that Kai and Mei were talking about going to Land together when Asami was there as well and that is not what their conversation was about. She twisted their words to plant doubt in Yamato resulting in him getting angry and ignoring Mei. He could have straight out asked her about it but instead he asked her some round about questions and didn’t even wait for her answers. I guess his jealousy is something else.
Megumi added the next blow by giving Kai tickets for Land after overhearing that conversation. Kai is the only one to continue talking to Mei when everyone else seems to have stopped. Megumi knows what she’s doing, inviting Asami to hang around with ehr and approaching Aiko as well whilst giving Mei looks. She’s so petty!
Kai also confesses to Mei and gives her Land tickets to help her feel better since she was crying over feeling lonely. This leads to problems with Yamato but that, luckily, is quickly solved. Kai understands that Mei and Yamato love each other and he is happy with that. He knows Mei won’t return his love but he still helps her out and knocks some sense into Yamato. Kai’s such a nice guy. Shame he came towards the end of the anime so we don’t get to see a lot of him.