It is a leading move. If the thrown dagger (which i still don't get how it doesn't end the fight considering Nagi's skill and Kai's lack of knowledge so he won't hit a dagger that's not even aiming for him) misses, the dagger will create a puddle from which the shadow beasts come out (like he did vs ikki), and he throws several daggers at once btw, almost never using 1 dagger. Summoning is faster than anything Kai can bring up.
Ikki Kurogane is basically a better Kai (faster, stronger, more skilled and had knowledge on Nagi's abilities), yet he still had to fight shadow monsters. And something i forgot to mention cutting down the beasts will result in black fog which will help a lot in Nagi trying to get behind Kai.
I believe it's when he says "With your chi i can finally return to the mortal realm". If it were just teleport from anywhere to any place he would have used it a LOT more often. He specifically said that he would return to the mortal realm and "NEVER" again used it. An ability that potent would have a lot more use.
Not really. By physical i meant, sword clashing. He would never go for that he would either assassinate, stab or send to the shadow room. Teleporting behind Kai is point blank range, he can literally summon himself from Kai's shadow ffs. Stabbing the shadow is far faster than Kai turning around for a couple of reasons:
1. As i said Nagi summons himself from shadows, he can literally come out from Kai's shadow and insta stab that would barely require any time considering he can just take his hand out from the shadow room and stab Kai's shadow before fully coming out. Yes he can appear only partly from the shadows.
2. The shadow doesn't move if Kai turns around. The shadow moves when the character moves, not when he turns around, the shadow is the same from turning around.
3. Nagi can still throw the dagger from Kai's blind spot.