545 I know

Apart from the ace cards and other one-time use cards, there were some cards he could use immediately as well.

Saki's chocolate awarded him with a [Random draw shard card], which he could exchange for fifteen random draw shards. Mayuzumi's chocolate awarded him with the exact same item, which basically meant that he received an extra thirty random draw shards.

Rion and Kotomi's chocolate rewarded him with two [Item Exchange] cards. Each [Item Exchange] card allowed him to exchange up to ten items he didn't want for an amount of points based on the item's value!

This [Item Exchange] card was something he found really useful right now after obtaining so many items. However, he would only be able to exchange a total of twenty items for points…

'System, can't you be a bit nicer and buy back my useless items like a proper shopkeeper would?'

System: "Hmph." (As imagined by Seiji).