Japanese investment firm Metaplanet has purchased more Bitcoin, bringing its stack to nearly 400 Bitcoin and sending its share price on a 5.9% rally on the Tokyo Stock Exchange. The firm said on Sept. 10 that it purchased 38.46 Bitcoin (BTC) for $2.1 million (300 million Japanese yen) bringing its total stash to 398.8 Bitcoin — worth $23 million. It’s Metaplanet’s tenth Bitcoin purchase since its first on April 23, according to Bitcoin Treasuries data. Metaplanet is down 13.3% on its total Bitcoin investment, as the cryptocurrency is currently trading at $57,520, up 1.5% over the last 24 hours…