Bonus Keys
Bonus Keys are special items that can be given to you at random via the present box upon A-Rank clearing or higher a Featured Quest with the present icon on any difficultly.
You can only receive one present per Featured Quest Ship wide for a total of four presents per day and you're not always guaranteed a key.
The present rolls are doubled if a player with the returner status who has not played for a month is within your party.
Most Bonus Keys expire 168 hours from the time it was obtained, however, Bonus Keys from campaigns often have different expiration durations,
such as a month from when it arrives in the mailbox.
Expired Bonus Keys can be recycled at a rate of 5 Bonus Keys to 1 Bonus Key Tokyo [Gold] Key,
however as of the time of writing it is only 80% efficient (loss of 1 Bonus Tokyo [Silver] Key in EXP).