i am absolutely lazy with making packed lunch so usually i make rice, put some furikake (could be salmon, or anything really) some seaweed, a bit of salt and wrap it in some cling film. not exactly the most balanced meal but throw some hard boiled eggs and some fruit you got yourself a quick and heathy lunch.
but sometimes i usually just put the onigiri in my bag and eat it whenever lol. no need for a lunchbox.