I have no idea how to time this move, the only time I can pull it off is where the ultra comes off so close to the kikoken it overtakes it, is there no way to use it as a sort of hit confirm?
Well what kikoken are you using and from what range? The easiest way to do it is off lp or mp kikoken since they move the slowest, giving you plenty of time to charge hosenka, and see if it hits, and then on hit do hosenka. It’s worth nothing that the total damage of eitehr of these I believe is less then a straight hosenka, but obviously the point is to fish for a guaranteed hosenka off the hit confirm. I’ve gotten ex kikoken to work as well, but from pretty far away so I had enough time to charge the hosenka. I admit I haven’t gotten it to link off hp kikoken, but its possible my hosenka input is just too slow. Regardless, with the first two you definitely have plenty of time to see if it hit to decide whether or not to go for the hosenka and still get it to link.
Edit: Its also worth noting with the ex combo that because ex kikoken knocks down now, they are considered air-borne, so you’ll need them near the corner to get the full combo, and even then the damage will be dramatically reduced do to the hosenka air combo damage nerf Chun got in USF4.
Edit2: Just tested in training room and I was able to get hp kikoken to link too, but had to do it from like absolutely maximum hp kikoken range in order to have enough time to charge the hosenka. Still find lp and mp more useful for confirming to hosenka since the slower speed give you a lot more time, even at closer ranges,
Also helps if you use the quick charge method on the kikoken- charge back, forward then quickly hit back + lp/mp/etc. This allows you to start charging a bit faster.