I know this was posted a few months ago, but it just worked for me (got both Matsukaze and Four Guardians in one run). I had not played the game for a year and a half, and deleted my previous save file at the time, so I had to start fresh to finish my last 3 achievements; Osaka is currently the only one I need now.
I didn't really need to alter his strategy, as by the time I cornered the last fief I just needed to delegate a couple more times and was good to go. Then I finally moved onto spamming Benefaction but finally got the horse.
Follow what the TC says as closely as possible and you'll have these 2 tricky achievements.