In the Shin Getter Robo manga, Benkei performs a heroic sacrifice which was arguably just as awesome as Musashi's sacrifice since he was on fire.
In Shin Getter Robo Vs Neo Getter Robo, Michiru Saotome, Genki Saotome and Benkei Kuruma all show up in the credits of the final episode (the Saotomes were absent throughout the series and Benkei never showed up due to Getter Robo G getting averted).
In Getter Robo Armegeddon, he raised the amnesiac Genki Saotome and called her Kei. During a battle with Shin Dragon, Ryoma shields Shin Getter with his Black Getter which causes it to be seriously damaged. Both Shin Getter and Black Getter are then forced to return to the Tower for some repairs. Hayato and Professor Shikishima proceed to ram the Tower into the Shin Dragon. Doing so kills Professor Shikishima before he reveals the connection between Go and Shin Dragon. Hayato manages to survive and Shin Getter is once again piloted by the original team. The Shin Dragon managed to survive the ramming and Saotome, Stinger and Cohen decide to personally sortie in a Mechabeast Dragon to deal with the Shin Getter once and for all. After dealing damage to the Mechabeast Dragon, it just heals itself as Saotome says that it can't be defeated as long as it's connected to the Shin Dragon. The Getter team are then trapped in a dimension where they are haunted by the spirits of Musashi and Michiru. The real spirits of Michiru of Musashi soon appear and break the illusion that the Getter team are trapped in. After knowing the truth behind Michiru's death, Hayato and Ryoma are back to normal and Benkei is encourage by Musashi to continue to look after Genki/Kei and take the fight to outer space after beating Saotome.
After a long fight with the Invaders in outer space, Ryoma, Hayato and Benkei sacrifice themselves to take them out once and for all with a Double Shin Shine Spark. The three of them are then thrown into Getter Valhalla where they are welcomed by another version of Ryoma. They fight with their other counterparts against numerous foes forever.
New Getter Robo has Benkei Musashiboh, the third man and The Big Guy of the Getter team. He has traits from both Musashi, the original Big Guy, and Benkei, the one who replaced Musashi after his Heroic Sacrifice. He's a wild man raised by Buddhist monks who sworn vendetta against the Oni for massacring his group. He carries a sword connected to them, and pilots Getter-3. His sanity was the reason why the professor picked him for the team. He wanted to destroy the Getter when he learned of the possible future. Also, he balanced out Ryoma and Hayato.