The main disadvantage of trading with MIKI is its lack of an English-language interface, which could be a significant barrier for non-Japanese speakers. Furthermore, MIKI charges brokerage fees for both domestic and foreign stock trading, which can be high, particularly for smaller trades. The fee structure is also somewhat complex, with fees based on contract price ranges, making it potentially difficult for new traders to fully understand. If you're considering a MIKI login, it's essential to consider these potential drawbacks before proceeding.