Trying to split a trip between Malaysia and Japan for the summer, has anybody who has been to either have any advice/tips?

Sorry if the question seems a bit general ^^

I'm a Muslim medical student who will be free over the summer with a pretty fair budget. I was planning on spending some time visiting both Japan and Malaysia (two places I have wanted to visit for sometime).

Initially, my plan was to spend two weeks in Japan and 3 weeks in Malaysia; but I've been getting mixed messages from various friends and family members and wished to get some advice here before planning out an itinerary.

What do you think is a reasonable amount of time in both? Especially for someone who wishes to experience various cultural aspects while also indulging in the city culture?

Thank you!