How to buy a ticket for the Lake Suwa Fireworks.
I will be coming from Intercontinental ANA Hotel at Akasaka and arriving in Japn on that day.
You do not need a ticket to watch the Lake Suwa Fireworks. There is plenty of open area around the lake where you can sit and watch. You may want to bring a small tarp or cushion with you as most of the area around the lake is grass. I recommend sitting in one of these open seating areas (accessible on foot from Kamisuwa Station).
Some prime locations require tickets to enter, most of which are decided by lottery a month or two in advance of the fireworks festival.
There is one reserved area (see portion highlighted in blue) that you can purchase tickets for on the day of the fireworks. Tickets are being sold at 19 stores around Lake Suwa, including the Family Mart convenience stores outside of Kamisuwa Station and the Suwa Heiando bookstore.
Also, please bring rain wear with you as the weather may change suddenly during the festival. The past few years have been quite rainy.
I hope that helps answer your question. Let me know if I can help with anything else.