Northern Honshu (ToHoku)

I will visit Japan in May and am looking into the only region that I have never been visiting before: Northern Honshu (Tohoku) region.

There is not a lot of tourist information available, probably due to the tourist popularity. My understanding of the area is there are lots traditional craftsmen and Morioka was selected by New York Times as one of the 40 best places in the world to visit.

Please advise some tour gems / itineraries to me. I can spend up to 4 weeks in the area.

Thank you.

Tohoku region is a vast area, depending  what your interests are, you can easily spend weeks there.

Without meaning to sound nasty I would suggest that you start by looking at these pages

https://www.japan-guide.com/list/e1102.html
https://www.japan-guide.com/e/e2400_tohoku.html

I have only been to the places around Sendai (Yamadera, Matsushima bay etc) but they were well worth the visit. At some point I mean to return to visit Tono & to cycle some of the Sanriku coast.

Last year I visited Morioka which is a pleasant if unremarkable city with some fantastic food options, I'd happily return. We visited Kakunodate, spent the night there and visited Nyuto Onsen, bathing in the amazing waters of Tsuronoyu Onsen and really, loved the area, it's so beautiful.
We intend to go back there and spend much more time, I find the little I've seen of Akita prefecture to be gorgeous.
The Sanriku Coast is gorgeous, driving down from Hachinohe, there are many beautiful places, I really liked everywhere we went in Tohoku. Aomori, Hirosaki, Lake Towada, Oirase Stream etc. all beautiful.
Tohoku deserves a lot of love.

The first thing you might do is look through this site's info on the region:
https://www.japan-guide.com/list/e1102.html

There are far more good places than just listed here though. Each prefecture and major city has its own tourist guide on their official website also, and it is well worth going through to find a lot of places that are listed nowhere else. I have been to the region multiple times, and to my surprise, during my first time (pre-covid) there were naturally fewer tourists than other areas like Tokyo & Kansai, but I did see and hear a lot of other tourists (mostly Chinese) there too. Some of my favorite places include Sendai, Yamadera, Hiraizumi, Geibikei, Hachinohe, Kitayamazaki, and Hirosaki. To be honest though, Morioka while a good place to base yourself, had very little of interest at all.

The next issue is if you can rent a car. The area is loaded with some great places, but it is in general quite a rural and mountainous place, and only going by trains and buses makes it inconvenient or outright impossible to see a lot of them.

Four weeks is a very long time to spend - there are a lot of good places to see as I said, but with that length of time you might consider seeing other regions as well, if you haven't yet.