I'd actually already written up one article for the Group Sounds band The Tempters（ザ・テンプターズ）, and it was for their single "Kamisama Onegai"（神様お願い）, since it was covered by Hanae（ハナエ）as the ending theme for the anime "Kamisama Hajimemashita"（神様はじめました）. At the time, I only knew the leader Yoshiharu Matsuzaki（松崎由治）because he was the one who wrote and composed the song. What I hadn't known was that another member was Ken'ichi Hagiwara（萩原健一）. I've only known him as a rather intense actor on TV and in movies, but hearing that he had been quite the hellraiser during his GS days, I'm not really surprised. Managed to find this late 1980s footage above of him appearing quite dapper on an interview show.
To be honest, it's rather difficult for me to imagine these guys as hellraisers in those outfits seen in the thumbnail above, but hey, it was the 1960s. Anyways, fashion critique aside, "Emerald no Densetsu" (Legend of Emerald) was The Tempters 3rd single from June 1968. From what I had seen so far of the results of the band's first two singles, they weren't doing too badly at all. And yet, according to the J-Wiki article on their third single, Philips Records was a bit worried about getting out that next big hit, so instead of leader Matsuzaki taking care of the next song, Philips apparently recruited lyricist Rei Nakanishi（なかにし礼）and composer Kunihiko Murai（村井邦彦）to whip up Single No. 3. I'm curious as to how The Tempters took that news, but it couldn't have been all that bad since "Emerald no Densetsu" did get made and recorded.
For me, "Emerald no Densetsu" does sound like a typical GS song of the decade, but apparently, composer Murai had taken in vocalist Hagiwara's suggestion of something with a mystique appeal, and created a melody influenced by French musical impressionism in achieving the goal of a certain mystery-laden romanticism. All of the fancy jargon aside, it was considered quite notable at the time for its use of strings, horns and oboe.
I guess lyricist Nakanishi had also taken that impressionism to heart as well since his words express a man falling in love with a woman represented by a glistening green lake. He even gets down on his knees to kiss it (was he wearing protection...y'know, for flesh-eating bacteria and the like?).
"Emerald no Densetsu" hit No. 1 on Oricon and became the 16th-ranked single of 1968.
Several singers since the original's release have covered "Emerald no Densetsu" including the group Mi-Ke in their 1991 debut album "Omoide no G-S Kujukurihama"（想い出のG･S九十九里浜...Group Sounds Kujukurihama of Our Memories）which peaked at No. 19.