2019年４月20日。
三角公園*1。習志野市本大久保１丁目。
*1:See also https://sumita-m.hatenadiary.com/entry/20150730/1438223216 https://sumita-m.hatenadiary.com/entry/20160901/1472698103 https://sumita-m.hatenadiary.com/entry/20170321/1490117707 https://sumita-m.hatenadiary.com/entry/2020/01/01/123253 https://sumita-m.hatenadiary.com/entry/2020/01/18/130200 https://sumita-m.hatenadiary.com/entry/2020/01/24/022136 https://sumita-m.hatenadiary.com/entry/2020/02/01/083510 https://sumita-m.hatenadiary.com/entry/2020/02/20/194810 https://sumita-m.hatenadiary.com/entry/2020/02/22/095246