Story said he sacrificed himself to make sure Kinemon can safe Momo.
On top of that it was implied Doflamingo is looking for Samurais.
Thats why both Raizou and Kiku are more suspicious to me. They were left behind before. Raizou could have contacted Kaidou before entering Zou, might even end up responsible for letting them shipwreck. Or it was the Well informed Kiku who stayed behind in Wano informing Orochi.
Incl. Udon plot my eyes are definetly on Kiku.
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At least this chapter will debunk my idea of Kaidou oiling and boiling BM. He know it did not work in Oden so he won't try it with BM xD