Visited these two onsen ryokans during Sendai sakura trip in 2009.
Sakan (伝承千年の宿 佐勘)
Stayed in this historical onsen ryokan in Akiu onsen town not far from Sendai.
Took free shuttle bus from Sendai station. Enjoyed in big rotenburo and sumptuous meals.
From its website, looks like some rooms have been renovated into modern style. Besides, it was the venue of the G7 meetings of Finance ministers and Central Bankers in 2016.
Stayed in this onsen hotel in Matsushima onsen, about 30min by express train from Sendai. It has quite a huge premise with a garden overlooking into the Matsushima Bay.