"I will keep this lesson close to my heart, and to my liver!" is a delightful line and a great translation-- I've kept up with the series for a long time, thank you for all the work and care you put into it!
I'm glad you noticed! I was a bit cheeky with it.
For those interested, what Shimomura says in Japanese is "肝に銘じました", literally "I will carve it into my liver". This is a fairly normal Japanese phrase that means to "keep something close to heart/remember something very well", but it's also clearly meant to play on the fact that the lesson is to do with beef liver.
There's no liver-based phrase in English that matches this meaning, but I figured I could tie it in to the 'heart', which is often used in English phrases.
