Tenkai (天海) refers to one of the listed subjects:
- Tenkai Nankōbō - Ieyasu's famous monk advisor who adorned himself in black robes.
- Amami - A character who shares the same spelling in kanji in Harukanaru Toki no Naka de 5.
- Heavenly Realm - A place in Harukanaru Toki no Naka de Yume no Ukihashi that happens to share the same pronunciation.