KKG
To help incorporate this mechanic from only being useful at lower ranks only. Shikyo members can also create jutsu that let them "rank up" their stat in question. This "rank up" in no way adds an actual rank up meaning someone A-3 does not magically become S-3, It simply means that the effect of the mechanic above WILL activate at the time the jutsu/item is cast and that is it. The same is true for two shinobi at SS-3, even though there is no rank above SS-3 the jutsu will still activate because they are considered an imaginary rank higher.
I dont think this clan needs this section, a stat interaction is a stat interaction, you can't fake having a stat higher without it being higher... while i see what you are trying to do, in having your interactions stay relevant at SS rank, our rules are that it caps at SS-3. sorry. If someone wanted to make a jutsu which gave them like an... X rank stat for a limited time, that would be up to their jutsu lists, i don't think you need to put it on the clan~
"Shikyo are also capable of accelerating to maximum speed without effort allowing them to reach maximum speed after their first step."
No, remove this please.
"They also have the ability to cast two jutsu at a time after the rank of Jounin."
Everyone can do this.
The rest of your KKG/ drawbacks seems ok.
Jutsu:1/ this is a scaling jutsu, you're not getting +50mp/s at C rank, no matter the chakra cost. Either give it one set value besetting its rank, or choose between this and your other scaling jutsu please.
2/ This needs to be C rank at the very least and have a drawback, the same as getting a +1. Also Why don't you just debuff your opponent? It would be so much easier.
3/ Seems okay, you say it closes in, at what speed? and im dubious about a jutsu which says it makes an opponent defenseless, that is up to how they block or what they're doing, i would like it removed please.
4/ this jutsu is fine, no ultimatums :)