I purchased these three years ago, and my child and I each used one. We stopped using them about a year ago because they couldn't connect to Vitality, so we switched to something else. I'm also considering selling them individually, in which case they would be priced between 2000 and 3500 yen each. I'm offering a discount for buying them all together. Currently, they all power on without any problems. They've been stored for about two years, so I don't think the battery life has deteriorated too much, but previously, some would last 3 to 5 days on a single charge, with one charge per day. The warranty has expired. Please understand that these are used items. I haven't initialized any of them yet, so please allow me some time to do that before shipping. I'm also busy with work right now, so it may take about 3 or 4 days, but I appreciate your understanding.