For Mr. Sherlock Holmes, a seven percent solution provides solace in times of intellectual inactivity, when the game's not afoot, and his brain craves for stimulus. On those occasions, he turns to a seven percent solution of cocaine injected into the forearm to compensate for the lack of vibrant mental activity.
Nearby, his ever faithful friend and trusted colleague Dr. Watson looks on in increasing anxiety, lest this morbid pastime lead to permanent damage in the tissues of the great detective's unsurpassed brain.
While the Japanese government most certainly does not possess the brain power of Mr. Holmes, it does seem to share his preference for the seven percent solution.