Elements

Graph of Types and Counters

The green checkmark means the attacker gets double damage.

The red cross means it only deals half damage.

???-Type

Cards that show ??? as the Element haven't been assigned an Elemental Type yet. WaifuGame leaves it up to the players to assign an Elemental Type to characters. 

In Season 1 of WaifuGame, Elemental Types won't matter because there is no (Manual) Battle mode. The Auto-Battle system only uses the Combat Stats to simulate the fight.

When Manual Battles are introduced (likely in Season 2), Elemental Types are essential. Season 2 probably won't start before the 1,000 most popular Characters have been assigned an Elemental Type by the community.