TKPGs (TK penguins) 🐧
If you are referring to a lone TK fan in the wider TK fanbase it would be: TKPG.
TKPG is a word that TK came up with probably with the help of his manager as they were marketing TK's penguin plushie merchandise from keychains to plushies. Later, while on Instagram as TK shared an Instagram Story with a song clip with "We are the penguins". It was clear he saw us as part of his penguins, his fanbase.
Therefore putting penguins and TK together made sense: TKPGs. In fact, over time online I find myself referring to TK's fans as TKPGs.
That TKPG. Hello, TKPG.
Now if you are asking me if there is a name for Ling tosite sigure fans as a collective. There isn't. The fanbase dynamics for the band are a little different than that of TK's much closer, personal solo fanbase. I personally think they attract different fans.
Fun Fact: TKPG can also refer to TK himself in terms of him through penguin branding. It represents him but us too, together. Which is what music is all about. Not cliques and power dynamics but everyone coming together.