Quote Originally Posted by Kratos
I don't think that the Oversoul used by Yoh to defeat Hao in the anime had anything to do with Matamune though, or any of the other things (aside from Chou Senjiryakketsu) that you mentioned; after all, they weren't even present in the anime. It was the Furyoku from all the other Shamans, or something lame like that.
Quote Originally Posted by ApocalypticARK
Uh... that was just Yoh using the super furyokou everyone gave him to make a supersized O.S. with the form of his main spirit, Amidamaru, with the O.S. weapon, S.O.S.
With the super furyokou he received from everyone, he just upgraded Amidamaru's original O.S. form, simply making it bigger and have better armor, plus being able to weild the S.O.S. (Which he needed to defeat Hao as explained below.)
Quote Originally Posted by ApocalypticARK
The S.O.S has a shape based on Yoh's very first spirit's, Matamune's, Chou-SenjiRyakketsu FumonGoryouE, O.S. Onigoroshi, a giant demon slaying katana O.S.
I wasn't talking about Yoh's Super Amidamaru form, I was talking about the Spirit of Sword (S.O.S.) and that Yoh copied the S.O.S. off of Matamune's Onigoroshi and combined it with Amidamaru's katana, giving it the red samurai armor, and neither Matamune nor the Onigoroshi weren't in the anime because the anime was stupid, but they WERE in the manga. As why he copied off of Matamune, Yoh was greatly influenced by Matamune and wanted to revive something from his long lost spirit friend, also because the Futsu no Mitama no Tsurugi was originally used to create the Onigoroshi, which had the power to defeat the great Onmyouji, Asakura Hao, and so the reason why Yoh's final O.S. form needed the S.O.S. was because it too, borrowing properties off of Matamune's Onigoroshi, had the power to defeat Hao. Again, none of this was explained in the anime because it was stupid, but they all were certainly explained later on in the manga, well, not the S.O.S. being base off the Onigoroshi, but it is obvious in how S.O.S. uses the Futsu no Mitama, and how after Matamune and his Onigoroshi was revealed from Yoh's flashback later on in the manga, Yoh's S.O.S. started to always show it's handle and the blade started to have the black and white edges of a katana, making it seem just like the Onigoroshi, unlike the anime's S.O.S. which never had a handle, and the blade always shown as opaque cyan O.S.
As for why I decribed the Onigoroshi as a demon slaying katana, it litterally means demon killer, and also mainly because when Matamune died, Asakura Hao turned his spirit into a Goryoushin, a type of spirit that protects its Onmyouji from evil spirits and Oni (demons), and was left with an artifact imbued with Matamune's furyokou from when he was alive, and also a portion of Hao's furyokou, which so far let Matamune's physical Goryoushin body last for more than 1,000 years without his Onmyouji master, Hao, and also let's him deploy his own O.S. to specifically slay Oni and in one case slay....don't wanna spoil it.