Garo: The One Who Shines in the Darkness episode 23

[Kamen Rider ShinkenRed]

Well if we take novels as canon presumably Kouga's son from one of them (Raiga I think he's called) became Garo after Kouga, but after that we've pretty much nothing, just at some point the armour wound up out of use and blackened. At a guess I'd say it's previous wearer died without a successor

 

[Hidden Masta]

He trained against Rago on an island for ten years and during his final fight with Rago, he pulled out the sword and killed him.

Maybe if he actually went to Makai training camp like all the other Knights he'd learn how to fight with the armor for more than 5 seconds.

 

[kanade_sakyo]

Well if we take novels as canon presumably Kouga's son from one of them (Raiga I think he's called) became Garo after Kouga, but after that we've pretty much nothing, just at some point the armour wound up out of use and blackened. At a guess I'd say it's previous wearer died without a successor

The short story doesn't say anything about Raiga getting the armor. Raiga is only a small child in the story. The other character who appear there is Kouga, Kaoru, Rei and Gonza, IINM

The cast and crew has already confirmed that this series is set in the future after the first two series during the pre screening of Soukoku no Maryu. So, even if Ryuga is related to Kouga, it's probably pretty distant relation