Yakuza Kiwami 2

Unlike in Kiwami, there is an achievement in this entry for unlocking every single coin locker. Coin Lockers are stocked with rare and valuable rewards but you have to find all the keys. Keys are not marked on the map via any element in game, so you will have to go to rely on maps below and just running into them on the street. The lockers in which you are opening are located to the left of the millennium tower in kamurocho and on the opposite side of the bishamon bridge to the cabaret grand. The keys can be seen because they have a sort of flash of brightness on the ground. The best help for this, at least when you're in the general vicinity of a key, is the locker key watcher. I believe its in the first locker you are available to open in chapter 1 in Kamurocho on tenkaichi street outside the Mahjong parlor. This item is helpful because it will emit a sound whenever you are extremely close to a locker key, close as in, within the immediate about 3-5 feet of your surrounding. It does not factor in height however, so just be sure to not run around looking for one on a roof. Overall, there are 100 lockers in total, 50 in Kamurocho, 50 in Sotenbori. For an in depth guide on each locker key and a great map and table you can check it out here: http://www.gamersheroes.com/game-guides/yakuza-kiwami-2-coin...

Credit to gamersheroes for the maps and guide.