Actually Mukuro is one of the three kings of the demon world so she is only a demon not both.

Two suggestions I am going to make are, add in 2 darkness approaches and take out good ref. My reason for taking out the good ref. is that every turn you can use Mukuro's effect to look through your opponents deck and it will be shuffled.

My opponents deck will be shuffled, not mine. Good Ref deals with my deck, not his/hers. I used to run 2 Darkness Approaches, and to be honest, it really doesnt make much of a difference in the game, so Im just going to keep it at one.

Oh yes, now I remember. Sorry about that mistake on my part. I guess it's true that darkness approaches really doesn't make that big of a difference. I was just basing that suggestion on what happens in the tournaments I go to. Since a lot of people run Kenko where I go to I like to run an extra copy of darkness approaches.

I would suggest Kayko's Promise ... becuase if your playing at Local tournaments wich you most likely are people will start running Time Freeze just to beat you.

It also can help agianst alot of different strategys like-
Ancient Tactics
Purgatory Koenma Decks
All You Need Is The Ground Suicide Decks
Genkai Dragons Victory Deck
Tainted Glare
Apocalypse

but realy its just used to stop Time Freeze and Stand Off and if used at the right time most likely a 5 discard.

Also I think that Rinku's Rush and Angelic Ambrace might be a good adition .... Ive seen people rush through there deck so just yama's are left play Angelic and Rush for an instsnt kill. Angelic also stops you from losing cards from Yama's and keeps a Roku deck in check for a turn or 2.

Hope I could help

-TheLegendaryKid