Like the another OVA of title, "Magical Heart Kokoro-chan", this is comedy. Unlike it, this isn't funny. You can say, "plot isn't so stupid and childish like MHKC, so why it's should be worse?" Because seeming seriousness completely ruins all its attempts to be funny, while the stupidity (the real one, not flashy as in MHKC) doesn't let to perceive it like a sensible story. In the end there is my favourite tune of title name inserted (no other word for this), which is the keynote, the summary of the original series, the expression of all the mood, all the characters hopes and aspirations... And it makes no sense, since OVA has no hopes, no aspirations, no mood but the silliest one.
The bottom line — Valentine Days is filler episode outside a series. It's not clear what this been done for, but if you've been so attached to the characters that any parting makes you suffer, this would fit as another dose... But how long can you stand it?
