Chapter 925 revealed two new Devil Fruit users among the Blackbeard Pirates.
Catarina Devon, known as the “Crescent Moon Hunter”, ate the Inu Inu no Mi, Model: Kyubi, a Mythical Zoan-type Devil Fruit that allows her to transform into a nine-tailed fox while 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.
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.
So, let’s just assume Suke Suke no Mi will not be affected by Observation Haki otherwise this fruit is just useless. What if Zoro is the only one in the world who can sense Shiryu? Not with his Observation Haki but with his sense for cursed things. We saw him more than once to sense cursed swords and even know where exactly they are positioned without actually seeing them.
So if Shiryu has a cursed sense himself or simply has a cursed sword (remember that 3 Kitetsu swords are not the only cursed swords) Zoro would be able to sense the invisible sword coming at him without actually seeing it.