Yes, HENK Comics & Manga Store is indeed open EVERY day of the year:
Monday 24 December: 11:00 – 19:00
Tuesday 25 December: 11:00 – 19:00
Wednesday 26 December: 11:-00 – 19:00
Monday 31 December: 11:00 – 19:00
Tuesday 1 January: 11:00 – 19:00
Special Holiday Opening Hours!