Ultraman Leo comes from Nebula L-77 (Leo constellation), and takes the human form of Gen Otori.
Ultraseven appears to fight a new foe, Maguma-sejin and his two "pets", the Red and Black Gillas. However, Magma badly wounds Seven, graphically breaking Seven's leg. Ultraman Leo drives off the foes, but Ultra Seven is confined to his human form because of his injury. The Ultra Eye is destroyed when Dan attempts to transform, and Dan takes up a role as the captain of Monster Attacking Crew. Gen is a gymnastics teacher on the side. Gen and Dan regularly train together, allowing Ultraman Leo to learn many moves in human form.
Mid-series, MAC is destroyed by Commander Black, and Dan vanishes, seemingly abandoning MAC. Gen spends most of his time later training the kids to defend themselves. When Commander Black captures Gen when he cannot transform, the kids kill Black in rage. Satisfied that the kids are able to defend themselves, Gen sails out to sea, his favorite student watching as he leaves.