This is TWO GAMES/CARTRIDGES in one box, along with the gameboy mobile adapter accessory. The games are Mobile Trainer and Mobile Golf. Both Japan-only games. Japanese text. They are made for the gameboy mobile system, for which the adapter is included. 

MOST IMPORTANTLY: The shells for these two game cartridges have been replaced. The game chips are original authentic chips (see photos), and the plastic shells were taken from other gameboy color games (authentic gbc shells). The stickers on the cartridges are reprinted, not original stickers, but they are very high quality. Everything other than the stickers and shells of the cartridges in this complete in box set is ORIGINAL. Everything other than the replaced stickers on the cartridges are AUTHENTIC.

Please note the mobile system has been defunct for years, so you cannot actually use it with an old mobile phone. It's just an interesting gameboy collectible.

The cartridges are functional otherwise. I believe they are saving, but due to the japanese text I am unable to verify. 

Includes everything you see in the first picture. Main box, Mobile Trainer/system box, Mobile Golf game box, cartridges, many inserts. The boxes have light wear but are in general very nice condition. The cartridges have a bit of wear, no label damage. The inserts all do not have any particular issues.