When my wife told me she wanted to visit a doll museum I wasn't particularly excited, especially when she told me would walk there. It's practically on the opposite shore of the lake from the station and I got less excited the more lost and tired I became. It took about an hour to get there. Once inside though I was glad we made the effort.
The museum displays the work of the accomplished doll maker Atae Yuki and I have to say his dolls are eerily realistic. The attention to detail is just amazing. My favourites were the passengers sitting on a tram.
You can see his work at the website below.
About 5 stops on the train line out of Kawaguchi-ko is the Mitsutoge stop.
From here, if you follow signs to the "Green Centre" you will pass an impressive waterfall before arriving at the start of the Mitsu-Toge-Yama trail.
The trail itself is relatively demanding due to the rugged terrain, and is very steep at times, but not very difficult to anyone with a reasonable level of fitness.
About half way up you will arrive at a location with 88 small Buddha statues all wearing the red aprons. From here, you will pass under a rock-climing wall before emerging at some huts near the peak.
Allow 4-5 hours for round trip if walking back to Kawaguchi-ko down the other side.