Shiryu of the Rain has eaten the Suke Suke no Mi, a Paramecia-class Devil Fruit which gives him the ability to turn himself and other things invisible. With this fruit, he is able to cut opponents without being spotted, taking them by surprise.
At first I thought it was a weird choice. It’s a very useful fruit for sure as it can conceal the user and anything he is in contact with, however, for New World standards my first impression was disappointment.
The reason for that is because: while obviously being hard to fight someone you can’t actually see, specially a skilled swordsman such as Shiryu, the whole point of Observation Haki is to feel the individual’s presence and every movement even while not seeing it.
Surely Shiryu has an advantage against lower level enemies, but considering his position within the Blackbeard Pirates the level of people who will go against him (like other Yonko Commanders, end game Zoro, Admirals..) should remain unfazed by his invisibility. So basically Shiryu hasn’t really gained much from eating the fruit. Fujitora is blind and still an Admiral so does it really matter whether or not you can see your enemy?
For this reason, it felt like a poor choice among every possible choice there could be at first, however here’s what I think about it now:
Suke Suke no Mi Awakening form allows the user not to turn everything around him invisible like some of the Paramecia Devil Fruits we have seen but instead it erases every trace of the user including it’s presence. This would make this fruit the perfect match for a blood killer like Shiryu. In this way he could have a chance against Mihawk.
From the moment Mihawk trained Zoro for 2 years I could see them fighting against each other by the end of the series but I could no longer see Zoro actually killing Mihawk to claim the title. I’m quite sure the two have developed a Master-Student bond even if Zoro refuses to even think about it.
So here’s what I think: Mihawk, being the current strongest swordsman and a former sparring partner of Shanks, will be taken by surprise by Shiryu (who probably lacks the raw skill and moral background to beat him in a honorable sword duel) along with his new ability cold blood murdering Hawk Eyes and claiming the title for himself and perphaps the Yoru as well.
*Theory by Icyveins04