So according to this chapter Tsukasa isn't Kaguya because the actual Kaguya is the masked girl, but she is probably someone who drank the elixir a thousand year ago. Now the big question is, will Nasa become immortal too or Tsukasa will find a way to age with him?
Of course, I'm also expecting that in the next 20 chapters Hata will give us hints that point to a completely different background for Tsukasa.