I spent a couple days in far northern Honshu; the weather was great and in some low-elevation areas almost every tree in the forest was in bloom – those slopes looked really spectacular. Saw one serow at 40.505629N 140.820258E. The best place for night walks is Oraise Gorge (40.53317N 140.97493E); in one night I saw True’s shrew-mole, J. weasel, masked palm civet (introduced), J. giant flying squirrel, large and small J. mice, and Anderson’s red-backed vole. Looks like rodent numbers in Honshu are picking up after a slump of last fall. Fields near forest edges were completely dug up by J. field voles, and numerous predators were hunting them at night; with a thermal imager I saw dozens of red foxes and raccoon dogs, two distant badgers, and one marten along Akita Hwy south of Lake Towada. Japanese squirrel was common, even in isolated clumps of trees and on brushy slopes; try Towada Shrine (40.434306N 140.893629E).
I checked out Ryusen-do Cave (39.860205N 141.796921E, 8:30-17:00 Nov-Apr, 8:30-18:00 May-Oct., iwate-ryusendo.jp). I was thee at night so the main entrance was closed, but I explored a side entrance about 20 m to the left (accessible by climbing a short switchbacking trail) and saw J. long-eared bats, plus lots of greater and least horseshoe bats.