Nakanoshima is on the south bank of the Kinokawa. I googled Na
ganoshima in hiragana, but I found nothing... Nakanoshima usually means an island in the middle of two or more rivers, and perhaps it was in the past. Osaka has a business district named Nakanoshima too.
The JR Hanwa Line (阪和線) has Kii-Nakanoshima (紀伊中ノ島) Station to the north of JR Wakayama (和歌山) Station. Note that Kii Province (紀伊国) is the old name of Wakayama Prefecture.
It's not far from JR Wakayama, Nankai Wakayama-shi, and the castle.
Google map
Wakayama City - Wikipedia
City Government