Yuki Yamada is going to reprise as Joe Gibken / Gokai Blue in Ryusoulger in commemoration episode to pass the torch from Heisei to Reiwa's First Sentai Team → Ryusoulger.
It is not known how Joe Gibken will connect to Ryusoulger. Only thing I see can see is that Ryusoulgers are Knights and they should be good with swords. When it comes to Joe, I have an image that he was pretty good swordsman among the Gokaiger.
It is not known why it is Blue instead of Red. But one theory is that Gokaigers can be consider as one of the unique Sentai teams of Heisei who can connect to any Sentai in any story like we see in Zyuohger or Strongest Battle. Since we have already seen the reprisal of Luka & Marvelous in Strongest Battle, the producers might have thought that it might be good to introduce Gokai Blue / Joe Gibken this time.
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