I loved this story too and agree, mature Nico is the best. Sometimes you gotta be the senpai and not just the loli tsundere. xD
From what I get Nico put the ring on her as a surprise.
But I have a question for someone who might know: does a ring on the pinkies have some special meaning for yuri couples? I think I saw this on a couple of yuri mangas...
Well a ring as a gift will always have special meaning if it comes from the person you love and I think Nico gave Maki a ring because she want to give something that would show how much she love her and a ring is the perfect gift for that :) and yep in the Girlfriends manga Akko gave Mari pinky ring too as a christmas present
Yes, it was in Girlfriends. And also in Akiko Morishima's "We're Aiming for Love Now" where the ring on the pinky is very noticeable. And maybe in others I don't remember now.
There's also the side that if they're trying to keep their relationship secret, in this case due to both gay and idol, putting it on the ring finger would be WAY too blatant. A pinky ring would be looked at by others as a simple fashion choice, while to each other and those they choose to tell, it would be much more significant.
Yeah, that makes sense. But I was just curious if it had some hidden meaning, as it was not the first time I saw it. ^^'
Plus in Japan the pinky finger is used to represent a girl, so maybe my brain was just trying to connect inexistent dots. xD