Kagome, Shippo and others in “Unfinished Business”

Kagome

You did it, Inuyasha! You discovered Tetsusaiga's secret and now you can master it.

Shippo

So does that mean Sesshomaru is dead?

Miroku

Most likely. I don't know how he could have survived. He received a direct blow from the fully empowered Tetsusaiga.

I didn't see Inuyasha make a direct blow. All he did was widely swing his sword around because his eyes were blinded with poison.

Inuyasha

What are you trying to say?

Listen, Inuyasha. You've uncovered the Wind Scar, I'll give you that much. But it now means that you now know what you're brother knows. You're still not his equal, and now he's even more formidable than he was before.

Miroku

You referred to him as though he were still alive.

Sesshomaru is still alive, and even though he despises the Tenseiga, it protected his life.

Sango

It protected his life?

Shippo

Do you mean that Sesshomaru is still around somewhere?

Inuyasha, when you used the Wind Scar against Sesshomaru, you didn't feel it strike him, did you?

Kagome

Is that true, Inuyasha?

Inuyasha

Hard to say. I was blinded. His body felt like it disintegrated in the blast from the Tetsusaiga. I didn't pulverize him or nothing. He just sort of disappeared...evaporated.

Tenseiga protected Sesshomaru from the power and might of Tetsusaiga. It acted on its own accord.

Kagome

It has a will of its own?

Sango

And here Sesshomaru calls Tenseiga a useless sword. And despised it as his birthright.

Miroku

Tenseiga is the sword of life. And when Sesshomaru's life is in danger, despite his dark soul, the Tenseiga choose to save him. And that is what makes him invincible.

So how do you defeat a foe like that? I wouldn't know how to. It's beyond me.