That's them back when he first confessed. They only came out on her back at that timeTsunderes are often described to have a prickly exterior, but this is the first time I've seen it interpreted literally.
Her spikes didn't come out in front at the end, that's progress, I guess? He should take that chance at the end to kiss her.
Well, if the spikes only come out when you’re with someone you love…Bruh if it kept happening in generations how did her family keep breeding lmao. There must be a cure then!
Oh no! I had blissfully not noticed that option, thinking they just made it work somehow (maybe the male sacrificed his life? For some generations several mates/times as it's not that easy to get pregnant?). But you must be right...Well, if the spikes only come out when you’re with someone you love…