Japanese Wedding Customs

Recently went to a friend's wedding in Japan and was not aware of the customs, learnt that you are advised to give wedding gift money in a specialised card envelope (commonly found in department stores or conveneince stores like Lawson too) called shugi-bukuro.

You also should only pay in odd numbers such as $300, avoid even numbers like $400 because it may suggest a 'split' or their marriage can break apart, super interesting...