A fan of the manga and anime series, Hayate no Gotoku
, bought 398 copies of the magazine Shounen Sunday
. The issue came with a free card from the series' trading card game of the character Sakuya. The number 398 is apparently a play on the character's name, the reason why the fan bought that amount of copies.
To complete his task, he visted 82 different 7-11 convience stores. In each store, he would leave a few copies for others to be able to purchase a copy of the magazine.
Source: Comi Press