Tokyo-listed investment firm Metaplanet has added another $7 million worth of Bitcoin to its treasury.Metaplanet continues its aggressive Bitcoin buying spree, acquiring 108.8 BTC.The company now holds a total of 639.5 BTC, equivalent to approximately $40.6 million at current prices.Metaplanet aims to hold on to Bitcoin for the long term, following the strategy of companies like MicroStrategy.