GR-KURUMI is the reference board that incorporates the RL78G14 (Renesas 16-bit low-power consumption MCU). Compatible with Arduino Pro Mini, this new board can use existing sample codes, ensuring easy use with Arduino language and standard libraries from both hardware and software aspects. WIZnet has 3 kinds of ioShield and ioShield-K support GR-KURUMI. Below link is the Japanese Renesas gadgets user’s posting about ioShield-K and he could the Ethernet application easily.
All materials about ioShield-K are on the Wizwiki.net