Explore Central Honshu
Beyond Tokusawa the serious hiking begins. The steep hike up the “Matterhorn of Japan” (so called because of its craggy appearance) to the mountain huts at Ichinomata on the lower slopes of Yari-ga-take (槍ヶ岳) takes around five hours, and can be done in a long day from Kamikōchi. There are basic huts on the mountain for overnight stays; a futon and two meals cost around ¥8000 per person, but things can get very crowded during the season.
Reaching the summit of Yari-ga-take may well give you a taste for mountaineering. The popular route to follow is due south across the alpine ridge to Hotaka-dake (穂高岳), the third-highest peak in Japan, a three-day loop that will bring you back to Kamikōchi.
Even for day walks, make sure you pack warm, waterproof clothing, as the weather can change rapidly in the mountains. At the height of summer temperatures on the peaks can be freezing, especially early in the morning.