Upvote:3
Does no road connection to another convenience store count too?
There are two Outlying Islands which have just a single convenience store: 東莒 Dongju and 綠島 Green Island.
The 7-11 on 綠島 Green Island is 32.15 km from the nearest one in 臺東 Taitung.
The 7-11 on 東莒 Dongju is 21.65 kilometers from the closest Family Mart on 南竿 Nangan.