Overnight in Kakunodate

I have an idea to travel from Aomori to Sendai with an overnight stop in Kakunodate. Leave in the morning, change trains in Morioka and then onward to Kakunodate. I can spend an afternoon there, overnight and wander some more in the morning and then leave in the afternoon to Sendai?

This will be in October- a Sunday.

I have 1 night to spare and Morioka has nothing that interests me on my way to Sendai.

Sure. Sounds totally doable with Shinkansen

Yep, you can take the Akita Shinkansen to Kakunodate from Morioka. Depending on which part of Oct you'll be there, you might catch some autumn foliage scenery too.

Akita Shikansen:
https://visitjapan-vegetarian.com/the-best-seats-on-the-akita-shinkans...

Kakunodate:
https://visitjapan-vegetarian.com/kakunodate-akita-japan/

Kakunodate has some worthy samurai houses to visit as long as the traditional birchcraft musum.
October is probably too early to see autumn colors in the town center (like last October during my trip), but maybe you can get yourself some at the nearby Dakigaeri gorge that can be visited via the city shuttle service.