@juicius I can't read Japanese so take this as you may, but given what you provided there, it sounds like "I'm glad I let it soak in" would work better. As in she went ahead and put the egg (and looks like soy sauce) over the rice while he was showering, letting it soak in, instead of waiting for him to do it right before he ate it. I believe the normal method is to put the egg on right before eating.