he is chinese, not japanese (douyin is the chinese version of tiktok)
this is pump it up (middle and diagonal arrows), not dance dance revolution (vertical and horizontal arrows)
yes this game can be played with 1-3 players, however when theres more than 1 player the colours of the arrows change so each player follows a different colour. this is the default colouring (yellow for middle, red for upper diagonals, blue for lower diagonals), which means this is meant for one person and is probably a custom map for people like him lol