The reason he has had the game running this long is that he doesn’t want to lose his save data. To explain, some old game cartridges used Static RAM (SRAM) with lithium-ion batteries. This meant that the cartridge could hold your saved data with the SRAM as long as the battery stayed charged.
The SNES cartridge for Umihara Kawase used this hardware to keep hold of a player’s save data. And so if this Japanese fan were to turn the console off or take the cartridge out it would eventually run out of batter and that data would disappear.
In one tweet, the fan says that he reckons the game has been running on the SNES for over 180,000 hours over the past 20 years. That sounds unbelievable and, indeed, he has been questioned on the viability of this.
Apparently, he doesn’t recall any blackouts happening in his house so that hasn’t affected it. He also says that he did have to turn the SNES off once in order to move house but he got it back on again before the cartridge lost its battery.
True or not, it’s safe to say that this is one of the most dedicated Umihara Kawase fans in the world. He’s just picked the game up on PlayStation Vita too.