This is honestly one of the most satisfying endings to a manga I've ever seen. The only thing I'm left wondering is if Taiga's dad or Arima ever realize(d) who the other was, but I think that's a good thing to leave up in the air. There's also the thing with Arima's gender, but I think it's pretty clear that he's a man. He specifically notes feeling happy getting to be a man around Taiga.