DMM Bitcoin Co., the operator of a Japanese cryptocurrency exchange, said Friday that digital assets worth at least 48.2 billion yen ($300 million) have disappeared for an unknown reason. The Tokyo-based company under major IT firm DMM.com LLC said it detected the abnormality at around 1:26 p.m. the same day and suspended operations such as withdrawals of virtual currencies and the reviewing of applications for new accounts. The amount of lost cryptocurrency is believed to be the second-largest ever in Japan, exceeded only by the 58 billion yen stolen from the Coincheck exchange in Tokyo in a …