When I first read this chapter, I thought, by knowing his sword, it meant they have fought in a war before.
And boom, nope. He is alive.
The fact that author has been playing low with immotals after a while really catched me off guard. (The first was That Robot male scientist, the second was Kintoki and maybe more)
Come to think of it. There is quite a few 'special power' in Gintama. By that, I mean something magic like. Such as, Those Mikos. The other immortals usually has a mean through technologies.
Utsuro was the one who has 'natural healing' power, magic like. which probably haven't re-introducted until this moment.
Well played.