largest city: Sendai / prefectures: Aomori, Iwate, Akita, Miyagi, Yamagata and Fukushima
Due to Tohoku region is located northernmost part of Honshu, spring in Tohoku is later than in Tokyo. Therefore, recommend to visit southern part of Tohoku, for example Aizu region of Fukushima prefecture. Aizu-wakamatsu is the most populous city in the region which has famous Tsuruga-jo castle and Higashiyama hot spring.
Hiraizumi is a town in Iwate prefecture close to prefectural capital, Morioka. Chusonji temple in Hiraizumi is a UNESCO World Heritage site and its Konjigido pavillion is the highlight of Hiraizumi.
Risshakuji temple in Yamagata, known as Yamadera. Yamadera literally means mountain temple. You can enjoy the stunning view from the temple.
Matsushima is a group of approximately 260 islands located in and out of Matsushima bay in Miyagi prefecture, not so far from Sendai. It is one of the three most beautiful views in Japan.