I think Sylvan and MianMian would really get along! Sylvan stuggles with academics so I think MianMian would try and help her study and understand things she's confused/unsure about. Also I can imagine Sylvan sneaking her sweets as a way to show gratittude, knowing about her sweet tooth! Also I think they could help each other grow like MianMian learning to open up more, and Sylvan finding better ways to manage her studies without losing sight of her dream. Also like Sylvan, MianMian seems to be really fashionable (love the fit girl) so Sylvan could make some clothes or accesories for her!!
For Hiro.. I think it could take a while for either of them to talk to each other but once they do warm up to each other it'll just be.. WAIT I THINJ THEIR FRIENDSHIP COULD BE SO CUTE! like Hiro wordlessly offering MianMian her favorite sweets when she seems down, or MianMian quietly standing by his side when he doesn’t want to face the world. They wouldn’t need to talk much to feel at ease with each other. Just sitting together, studying, or sharing snacks especially sweet since they're both a sweet tooth
OOPS- I THINK I WROTE TOO MUCH