Yes it will cost holy soul points; Shingen's the final soul in the Yukimura-Masamune series.

It seems like that at some point, the orichalcum exchange on DMM got updated. In addition to the raid SSRs, there's now one new SSR for each element. 1 ori for 1 copy, as opposed to 2 ori for 1 copy of a raid SSR. They do seem to have worse stats than other SSRs (some having atk as low as SRs). But they do come with two skills. The one for light as well as the one for water seems interesting. For starters, the light one's a glaive instead of a type that light already has a bunch of (water's Yet Another Hammer, boring). But more interestingly, their second skill is an Ascension type. The light glaive has it at medium and the water hammer has it at large, apparently.

Ascension is one of the newer weapon skills; it's basically +healing (raises healing amount and healing cap of skills by the respective element). Ascension (small) raises by (4 + skill_lvl)%. Medium is 7 instead of 4. Ascension effects stack on top of each other additively. Also, apparently there is a cap on +healing of +200%. Either that was discovered through union events (most likely), or someone actually put together enough weapons with ascension of the same element (I'm not even sure if that's technically possible yet!).

Ascension effects stick out to me, as they're not all that common. Especially natively (instead of being tacked onto an older SSR through final limit break). And moreso, through guaranteed methods (ie not through a gacha).