Discovered this one some time ago and rather enjoyed it for its cute 1980s aidoru synthpop feelings. Images of "The Best 10" and Myojo magazines came flooding back into my head.
"Tropical Mermaid" was sung by 80s aidoru and seiyuu Yoko Obata（小幡洋子）as her 2nd single released in January 1986. The song was actually inserted into the anime "Mahou no Star Magical Emi"（魔法のスターマジカルエミ...Magical Emi, The Magic Star）, a show in which Obata starred as the main character Mai Kazuki who belongs to a family of magicians.
Judging from the light bleeps and bloops, I had assumed that "Tropical Mermaid" was another Haruomi Hosono（細野晴臣）tune, but in point of fact, the melody was provided by former Sugar Babe member and City Pop singer Ginji Ito（伊藤銀次）, while Yukinojo Mori（森雪之丞）wrote the lyrics. Quirky and perky, indeed.
The song also led off her debut album "Pearl Island" released in December 1985. Obata would release a total of 3 singles and 4 original albums up to the end of 1986, along with a BEST compilation in 2004. Obata, which is her real name, took on a number of stage names to release some more albums and singles up to 1992 until she left show business the following year to become a jewelry designer.
I've never seen "Magical Emi", but from what I can gather, I think Emi-chan probably was a bit more proficient at her craft than the young lady in "Tejina Senpai". 😁