The large electrolytic capacitor in the top-left corner has been seen leaking, causing minor corrosion. Unless it has been left unattended for a long time, repair of the corrosion should be very easy,.The capacitor is located at C901, and is rated for 2200uF at 25v.
Later CV1000 games, like Mushihimesama Futari, feature a bodge capacitor installed from the factory. Without this capacitor, the leading edge (i.e. bottom side when vertical) of a sprite's source data may have flickering pixels.The capacitor is an 0603 package 56pF capacitor. It connects between ground and pin 16 of the VRAM at U6.
If the CPU is stuck with the LED at D6 lit, pulsing every second or so to a slightly darker color, ensure that the SH3 RTC crystal at X2 is intact and oscillating. It is a 32.768KHz crystal. This is not to be confused with the RTC-EEPROM at U10, which has its own internal crystal.