Khu's Twitter title currently being "A new low for Kieran, says Khu" really makes me think that the Dipplin2 you get was once his (whether it's literally the one you fight or Kieran passes his second, likely also "'Dokutaro'-blessed" one to you).
In the meantime, part of me cannot shake off the possibility that Ogerpon's old trainer, who dumped the Tera crystals into the Kitakami lake, was a certain disgraced trainer with a deceased Cyclizar named
Lafcadio Heath, who visited Area Zero one more time after his fateful first trip there and beseeched Terapagos for a nice new buddy Pokemon to spend his retirement/exile with. Any evidence against that already in the Teal Mask?