All of this is pretty standard, it's just the random encounter in the middle of the street that's the issue. Switch it up so they're either walking by the old middle school, or the prestigious high school, and the encounter is suddenly less contrived since it's a place where this type of encounter might happen.
Is it random though? I think Glasses may have stalked Nagisa once she found out her school at the festival. Maybe Nagisa's dream school is on a similar route toward Mashiro's house?
But yeah, don't think Glasses girl is bringing up any new insecurities. They've been hinted at for a while. New player is just aggravating wounds that haven't healed. Mashiro's clearly mentioned she's a clinger. We thought, ooh cute. But really she's a deeply insecure individual. Sure Nagisa has time for her now but I believe she'd mentioned going to cram school, probably in hopes of getting in a good college to go to med/nursing school so she can be informed on how to care for Mashiro, so I imagine Mashiro might have a rough time making new friends in class.
Her old friends might get busy too, leaving her at the mercy of her insecurities. Remember, girl didn't really have friends before since she was always sick and there may have been a mention of people treating her differently/drifting away because they felt she was too fragile?
So yeah, new girl will probably come with a backstory explaining why she's in love/fixated on Nagisa since they only talked once? Maybe defended her from bullies? Hard to tell since the tone of this always felt feel good/romance vibes.
Hopefully Mashiro will become stronger and become an equal partner in her relationship with Nagisa. As cute as the boob hug is, I'd really like another sleepover with Mashiro helping a tired Nagisa to bed and giving her yet another kiss that Nagisa won't know about.
