I’d certainly like to see opinions on options and strategies people have used on this topic.

A friend and her young daughter’s first Tokyo visit will coincide with our next stay there in the Spring. They will be area hopping and trying out a range of budget accommodations. I’ve said we’d store larger luggage items for them (we’re all returning to London on the same CA flights - luggage allowances are 46kg each, am sure our cases will be groaning!).
Unfortunately, we won’t be staying close enough to each other to make this free storage service particularly handy or convenient for them AND we’ll all be off doing our own things for the most part. For this reason I am keen to learn about methods that have worked for others. Problem with travelling in Kantō with a child in Easter is that you need to be prepared for winter snow and scorching sun, makes packing light into a serious challenge.