In the series, I liked Adachi and Kurosawa's relationship more, but I think Minato and Tsuge's spin-off was better. I'm guessing it's because on the show we've seen the first couple's relationship develop, but we haven't seen it with the second couple. So in the spin offs it was turned around.

The Valentine's Day part was just an accidental explanation for the misunderstanding that was created after Kurosawa found the mysterious gift. Well, I agree it was cute.

The second part of the spin off revolves around Rokkaku finding out why Kurosawa often shows up unexpectedly when Rokkaku talks to Adachi. And it was actually funny.