Kain

Kain (カイン), also known as Kindness, is a giant orca whale UMA that has been tamed by Under. It acts as oceanic transportation for the group.

Appearance
Kain is a giant orca whale, that is as big as a cruise ship in size. It's unusual in appearance compared to other orca, as it possess three eyes, four fins, and two tails.

Personality
Little is known about Kain's personality, however it appears to be very loyal to the members of Under, allowing them to ride inside of him and obeying their orders without issue.

Unrepair Arc
Kain carry's Creed and Feng to the black market auction yacht and spits them aboard at Rip's request. Later, when Tatiana begins to release UT Area, Creed and Feng flee the yacht and return to Kain offscreen.

At the arcs end, after Rip has been shot by Andy's Crimson Bullet, Latla summons Kain to rescue the duo, and then sinks into the ocean after doing so.

Union Arc
It shows up again as one of the quests offered by Apocalypse, where it is revealed to be an UMA known as Kindness.

Abilities
Transportation: Due to his immense size, members of Under are able to ride inside his mouth in order to travel across the ocean

Massive Lung Capacity: According to Fuuko, Kain only has to surface for air once a day. A normal whale, in comparison, needs to surface for air every 5-90 minutes depending on the species

Trivia

 * Kain ranked 41st in the Third Popularity Poll.