Unable to answer "What are the opening hours here?" – さいたま市立漫画会館 (Museum) – https://osm.org/node/1420166452 via StreetComplete 59.3:

休館日:月曜日(祝日の場合は開館)・祝日の翌平日・年末年始
The day after a PH is off.

Attached photo(s):
https://westnordost.de/p/252790.jpg