Here is their blog:
And their coming concerts are:
Seikatsu Sozo Kukan Nishi Lunch Concert by Omocha no Hako vol.61
14-40 Hamamatsu-cho, Nishi-ku
One minute on food from Nishi Yokohama Station, Sotetsu Line
February 26th, 2015
First part: 12:00-12:25
Second part: 12:50-13:15
Babies and toddlers welcome. You bring in your stroller.
Flat Kids Concert "A New Spring is Coming"
Yokohama-shi Seishonen Koryu Center (Free Flat Nogeyama)
2F Music Room
25 Oimatsu-cho, Nishi-ku
Charge: 500 yen (free for elementary school students and under)
Target: Preschool kids
Reservation required. Closed when it's full.
Signing in by telephone (Seishonen Koryu Center: 045-241-0673)