Tomugawa uses mainly Death magic The minion uses mainly Storm.
What you should do depends on what school of magic you belong to. In all cases, you should take out the minion first.
No matter what school you are, you'd do well to buy a few Death Shields (the 90% blocking kind) at the Bazaar. They aren't expensive. Put them in your sideboard and keep one on you whenever possible.
it helps to have life spells, whether they're healing or attack. if you don't have many healing spells, like me, and only a couple pixie cards in hand, attack a lot. if you have high pip spells, then attack rank 2 or 3 cards constantly, or save up pips. at least that's how i did it :) good luck! :)