There are lots of fish/seafood references in characters’ names and other things in Star Driver.
Takuto’s last name may be a reference to the Konoshiro fish: The following legend has been handed down about the name Konoshiro:Long ago, the a wealthy man in Shimotsuke province had a beautiful daughter. The governor of Hitachi provence made a marriage proposal upon setting eyes on her for the first time. But, the girl had a lover. So, thinking of their daughter, the parents lied to the governor and told him, “our daughter has died.” In place [of her body] they filled the coffin with fish, and conducted the cremation before the messengers. At that point, the contents of the coffin were starting to burn, and since the fish was the Tsunashi, one said to give off a smell like a burning human body, the messengers were all convinced the girl had really died and they returned to [Hitachi]. After that, the Tsunashi, which was given in place of a child was called “Konoshiro” (kanji: child’s substitute).Not a fish, but related to the above. Katashiro can be written 形代 which is very similar both in spelling and (literal) meaning to 子の代 (Konoshiro). Details on what a katashiro is here. 2ch’s speculating more toward the human-shaped type of katashiro or the literal meaning of “substitute figure.”
Agemaki is a kind of clam. (no Japanese page for this one.)
The North Maiden is nicknamed fish girl. One theory on 2ch is that her real given name is "Nanako" (魚子). Literally, it means "fish child" or "fish roe" and fits with the given name scheme of the other Maidens. A possibility for her surname is "Kinoto" (乙), which may have meant "fish guts" in the Chinese Shang Dynasty and is sometimes known as the fish hook radical. The letters for the East and South Maidens mean "weir" (a fence placed across a river to catch fish) and "[fish] hook", respectively.
The Yamame is a kind of salmon. (2ch was theorizing this is where Tiger and Jaguar’s last names come from since they’re Yamasugata and Sugatame and removing Sugata leaves Yamame.)
There’s a family squid called the Shindou-ika which the Aori-ika (the Bigfin Reef Squid in English), also known as the “King of Squid” is part of. Wikipedia lists this same squid as part of the Loliginidae (aka. Yari-ika, Spear Squid) family though. It’s probably worth noting that squids have blue blood (I figure this is pretty common knowledge, but I wasn’t thinking about it until literal squid came up). [EDIT] Did some more searching, this came up in the 2ch spoiler thread months ago and was quickly dismissed because apparently シンドウ (shindou-ika) is just a misspelling of ジンドウイカ(jindou-ika, which is actually a genus not a family). So idk anymore.
Keito's aunt's name is Goshiki, which is also a type of koi.
Somewhat related, Midori may also mean "waterfowl" (水鳥).