User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-73.244.39.60-20181115210530/@comment-162.252.126.39-20181121222812

"Why would Souji ever train Rias in swordsmanship?" you ask? Because she's a major japanese otaku. There's no way she wouldn't miss a chance to get a more hands-on experience of japanese culture, i.e. the way of the sword. And like i said before she probably stopped training way before the series, due to having to train in the use of her demonic powers and magic, to be more elegant, like a proper pureblood. But now after eveything that's happened(especially when cao cao sealed her powers that one time), she probably thinking it wouldn't hurt to have something else under her belt aside more magic tricks.