Okay! Our Illustrious GM has approved the Broad Strokes background, so I'm sharing it with the rest of you all so you know what you're getting into.
I'm going to preface this by saying he's not blind, or at least won't be as soon as his eyes heal, which will likely happen just before you all meet him...
Born Hiro, he was a gifted son of the Dragon's Investigator family until some manner of training accident cost him his sight recently. It will never fully recover.
Concurrently, the Scorpion Clan had been in negotiations with the Dragon on an unrelated treaty matter & had petitioned as a sign of good will for a marriage between a Scorpion & a Dragon
According to old lore, the Kitsuki Daimyo at this time hates the Scorpion clan. Unfortunately for him, Togashi basically said 'Suck it up, there's reasons. This son of your House will still be serving my will in this.'
To which the Kitsuki daimyo effectively replied 'Fine, but I don't have to like it! What about Hiro, he's blind now so it's not like he can do anything anymore?' And Togashi just smiles enigmatically...
So the Scorpion find out too late to do anything about it that the guy they're getting is blind, but they are now also not happy, so they marry him off to some technically spinster, almost-ready-to-retire-to-an-abbey, Soshi; but the important thing is he is now subordinate to the Scorpion & will to the best of his ability sniff things out for them now.
Something about how he carried himself through all the b+~+%!@! involved gets back to the Hantei (on a good day) & impresses him enough that he both invites Hiro to Otosan Uchi & makes it known that he's a 'good boy' & nobody gets to f&&$ with him, in a nutshell.