After chapter 943 came out, I noticed a lot of people thought that the character behind Kanjuro, in the first page of the chapter, is actually Izo, one of Whitebeard’s division commanders.
A quick reminder about Izo: he fought alogside Luffy at Ace’s execution and was confirmed by the Vivre Card to be from Wano. He was probably one of the participants when the remnants of the Whitebeard Pirates fought in the Payback War against Blackbeard. His fate beyond that remains unknown.
Now for the speculation.
In the panel of the meeting with Lord Yasuie, all 9 Scabbards are present. Even Denjiro and Kawamatsu are there as shadowy figures. The only one missing is O-Kiku and Izo is there in place of her. Oda obviously did this deliberately. If Izo is a former Scabbard who travelled alongside Oden, it explains how someone from such an isolationist country ended up being a Commander with the Whitebeard Pirates. Izo found himself at ease on the sea and with the Whitebeard Pirates, deciding to join them.
Which would mean that O-Kiku joined the Scabbards at a later date – that Izo’s replacement among the Nine Red Scabbards, as he left for the Whitebeard Pirates, ended up being O-Kiku.
And here’s the kicker: O-Kiku was more than once mentioned to be flat-chested and referred to herself as a male samurai. Wouldn’t it be pure Oda to make O-Kiku and Izo siblings: the brother a crossdresser who looks very feminine; the sister 3 meters tall, flat-chested and thinking of herself as a man. In one fell swoop Oda just foreshadowed that Izo is a former Scabbard who ended up being replaced in the Nine Red Scabbards by his own sister.
*Theory by ColangeloTheUsurper