Bitcoin is an asset to me and a type of currency. It being an asset is because it can be stored or hodl and in future be sold to get good profit. Also as a currency to make transaction for buying and selling on internet and online.
Bitcoin as an investment is already an asset where you can keep it for future purposes because the longer you hold it, the bigger your return of investment will be. The only difference of bitcoin as an asset to other assets that you can have is that bitcoin's value will change regularly from time to time because its value depends on the demand of people.