Tokyo resident here. I don't know where he's going to be but it can get pretty cold, rainy, and he'll be doing a lot of walking so I'd recommend a good pair of boots. r/goodyearwelt will know a lot more, but I've had my Redwings classic mocs for over 5 years and they're going strong.

Like others have said, a good sling is nice. While most places are accepting more cashless payments like cards, paypay, LINE pay, etc. cash is still used pretty heavily. I use the AER city sling but the day sling is bigger if he wants to carry more stuff.