Kelvin Stelar

Kelvin Stelar (Hoshikawa Daigo in the Japanese version) is a character from the MegaMan Star Force series. His role is like that of Yuichiro Hikari's. He is an stronaut who went missing a few years before the first game. He was captured by the FM-ians while trying to form a BrotherBand with them. But Omega-Xis turned him and his crew into EM waves so that they can survive in space but are lost.

He makes an appearance when Geo is fighting Andromeda. He encourages Geo to fight on because everyone counted on him. Later Kelvin appears in a dream, telling Geo to trust in his friends. In the Deep Space Comp, Geo also finds Kelvin's Transer, along with the Kaiser Knuckle weapon, and a message to Geo, explaining his fate.

Finally, in MegaMan Star Force 3, he is found to be inside Meteor G (as he had been converted to EM waves by Omega-Xis). Hope Stelar gives Geo the "Kelvin Code" (Daigo Code) which plays a vital part in the final stage of the game as it helps locate Kelvin's memories throughout the Meteor Server. At the end of the stage, Geo finds Kelvin standing in front of the core, only for him to be sucked in when the Crimson Dragon is summoned.

After the defeat of the Crimson Dragon, Kelvin calls out to the Hunter VGs of those gathered at WAXA who saw Geo off, telling them that Geo may not make it back to Earth, and his sacrifice was not in vain. This inspires the people of Earth all to form a Rezon group to help guide Geo back to Earth. Kelvin tells Geo to use the resultant Rezon Wave, but Geo is reluctant to, as Kelvin and Omega-Xis have no way to get back. As Geo unwillingly drifts back towards Earth, he finds a last piece of his father's memories left behind by Meteor G, and eventually hears the people of Earth calling for him. Without a regret, Geo rides the Rezon Wave back to Earth.

Some time after his return, Geo is seen watching the sky, thanking Omega-Xis and Kelvin for their efforts. Then, a shooting star is seen headed towards Geo, and it turns out that Omega-Xis found a way back. A second shooting star is then seen headed towards them... Later at home, Geo returns to his mother, revealing that Omega-Xis and Kelvin have made it back to Earth safely.

Manga History
Kelvin's background is the same as the game. After the tournament at the Wave Coliseum is over, Gemini Spark steals the Star Force to revive Andromeda,the king of the FM-ians. This story arc concludes with Mega Man discovering that Andromeda and his father Kelvin had fused as a single EM Wave Human. Defeating Andromeda, Kelvin is freed and returns to Earth to live with his family and new FM-ian friends

MegaMan Star Force (anime)
He appears after the final battle with Andromeda when Geo asks Cepheus to show him his dad. Kelvin says that he's safe in space, exploring other planets and might not be back for a long time.