Hello! Me and my friend Michiru have been summarizing and translating the stage plays that came out in recent years, and I'm going to share the links here. The plays are based on the newest, ongoing series of Mirage prequels set in the Shōwa era, ie. the lives Kagetora, Naoe and the others lived right before the lives of the main storyline.
While these are not full translations, and especially mine might be flawed since I am just learning the beginnings of the language, you should be able to get a pretty good picture of what is generally going on in the story. We have also added screencaps so you can enjoy looking at the great actors, too.
Here are the links:
1st stage play, based on 1st novel: Yonakidori Blues
http://michiru2042.tumblr.com/post/128310313517/mirage-of-blaze-yonakido... (part 5 has links to the previous posts)
2nd stage play, based on 3rd novel: Ruritsubame Blues
http://imperfekti.tumblr.com/post/144999813054/mirage-of-blaze-stage-pla... (in 10 parts)
2nd stage play's extra scene, based on the 6th book but chronologically set before the two stories mentioned above: Love Me Tender
Personally I loved the plays and felt they deepened the story and characters a lot. For example, we get to learn more about Minako, see Kagetora before he sealed his memory, as well as enjoy Kagetora and Naoe's dynamic in different social positions as their age gap is basically reversed as compared to the main story line. Also, seeing Kagetora and Naoe portrayed by real, live people also brings a whole new level of excitement to the whole thing, so I would like to encourage everyone to try to see the plays.
The DVD's can be purchased from here: http://www.shop-ep.net/trifle_stage/ While the company itself doesn't ship overseas, it should be possible to get them by using a shopping service.
The third play will be coming out this autumn, so let's look forward to that as well!
Attached: a screencap featuring Tomita Sho as Kagetora and Aramaki Yoshihiko as Naoe, and of the full Yasha-shuu.