The First 3-day Weekend
And so soon after the New Year Holidays.
The first shukujitsu* after nenmatsunenshi** Results in a long weekend almost immediately Said holiday is to celebrate turning twenty Or when Japan's "kids" reach maturity
Notes:
*Shukujitsu(祝日)= public holiday **Nenmatsunenshi(年末年始)= the four Japanese characters literally translate to "year end year start", respectively; it refers to the New Year Holiday in Japan
※This holiday is celebrated in Japan on the second Monday of January.