Place low-fat butter into small cubes in a heavy frying pan until foaming. Sprinkle the tuna steaks on each side with salt, pepper and minced sencha green tea leaves, add them to the pan and saute over quite high heat about 2 minutes.
Meanwhile peel and thinly slice the shallots. Turn the steaks and brown the other side, about 1 to 2 minutes longer. Strip the herb leaves from the stems.
Test the steaks in the center with a small knife, cooking them to rare or medium done depending on your taste. Transfer them to a plate, cover and keep them warm. Chop the herbs.
Add the shallots to the pan and saute, stirring, 1 to 2 minutes. Add the green tea and red wine and boil rapidly until reduced by about half. Off the heat, whisk in the remaining cubes of butter until it softens and thickens the sauce slightly. Stir in the chopped herbs and taste for seasoning.