SHISEI-DAYORI (City Info) July
The Kumamoto City Zoological and Botanical Gardens (and the rides) will remain open until 9 PM every Saturday between July 18 and August 22. Admission fees will be the same (300 yen for adults).
http://www.kumamoto-if.or.jp/topics/topics_detail.asp?PageID=5&ID=7920&pg=1&sort=0&LC=e
Reference, website of the ZOO http://www.ezooko.jp/one_html3/pub/default.aspx?c_id=22 (English page)