(videos will be posted later when I can find some good ones)
Mikazuki "Munechika" Seon (Kaiyoshima):
(normal) Dasoku (utaite).
(younger) Nero (utaite).
Kaito Shirai (Tiberius):
KAITO (vocaloid).
SS-A2 Miki (Mirainotochi):
SF-A2 Miki (vocaloid).
Yamanbagiri Kunihiro (Miyamoto Island):
Soraru (utaite).
Yagen Toushirou (Kiyosaki):
(normal) Seiichirou Yamashita (Touken Ranbu official seiyuu) or Yonezu Kenshi a.k.a. Hachi (utaite)
<-- sorry, the music video is weird af
(shota voice) Fukase (the vocalist of SEKAI NO OWARI)
Kirsten Leiffson (Greenland):
Nanna Bryndis Hilmarsdottir (the vocalist from Of Monsters and Men)
Ichigo Hitofuri (Awataguchi school):
Atsushi Tamaru (Touken Ranbu official seiyuu)
Mikage "Munechika" Seon (fem!Kaiyoshima):
Megurine Luka (vocaloid)
Yamanbagiri Nagayoshi (2p!Kaiyoshima):
Rib (utaite).
Shinano Toushirou (Sekigahara):
Kobayashi Yuusuke (touken ranbu official seiyuu).
Satsuki Miyaura (Daikiko):
IA (vocaloid)
Lon (utaite)