User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-36663391-20190823203205/@comment-2A00:23C6:4700:7B01:E163:5C43:2209:8328-20190823214449

I think the boosted gear also helped sacred gear evolve to the desires of the wielder similar to ryutenmaru. since issei didn't have any way to unlock great reds power i believe boosted gear and ryutenmaru may have helped each other to do so.