- Easy to see how Kiku could be suffering from lingering resentment and/or abandonment issues. Loses his bro, Oden skips out on Kuri, gets stuck with collecting intel while Kin and Co. leave in search of allies...and there's the matter of his father, whose imprisonment -- the exact crime committed thus far unknown -- occurred during the reign of the Kozuki. Would be quite the punch to the gut if turned out his dad was put away for the very same crime as Oden, the latter of which not only being allowed to return without penalty but also welcomed back with open arms ( minus some very brief grousing from some of the Scabbards ).
Or who knows, maybe he had a crush on Oden and became bitterly jealous of Toki or something lol? Would fit with the Hannya-like mask he carries and all it represents - the anguished, vengeful bitterness of a woman scorned.
- Concerning the whales' elation over a destined future meeting between the two kings, I'm guessing it relates to what the 2nd king, Joyboy, and whales themselves represent: Poseidon can be said to embody the Sea and Joyboy the Land, with whales symbolizing the union of both worlds; their ancestors having evolved from sea-life to land-faring mammals, then later "returning" back to the sea in their current modern forms to bring things full circle ( more importantly, without simply REVERSING the process...the revolution of the spiral and the progress it represents vs the stagnation of a spinning wheel and the lack of wisdom gained with a flat reset ).
On a related note, ever wonder what's up with the curious lil moustaches of Dr. Tsukimi and the Moon People's automatons? I'm willing to bet Oda used sea otters as the basis for their designs, for they too, like whales, are believed to symbolize the meeting of two worlds in various cultures.
On ANOTHER related note, recall the Wani or "Crocoshark" of Wano, as well as many other instances of the overall theme of "mixture" popping up throughout the narrative: hybrids ( Jack and possibly Kaido ); the chimaeric GIFTERS; inter pirate crew cross-pollination, ie Izou, Oden, CatDog ; wonky team-ups, e.g. Roger and Garp, Ninja-Mink-Samurai-Pirate Alliance, Kaido and Big Mom, WG and PIrates, etc; Wano's possible origins as individual islands combined by the Oars clan; the motley make-up of the Scabbards...
Really does seem like Oda's exploring far more than just the blurring and opening of national borders here, no? Plenty more examples of "hybridization" to come, I'm sure.