If the scene starts as fully yuri, but eventually a male comes in and joins them. (The “Male Involved” tag is only used if the male is involved from the beginning of the scene.)
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Rating: 4
The FMC tries to have sex with the same woman from Ch. 1, but she stops and pushes her off.
Later, the FMC tries again in front of the woman’s husband, who eventually joins in and it becomes a threesome.
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Rating: 4
The MC has a foursome with Saki, Shiki and their mother.
At one point, Saki puts on a strap-on and has sex with her mother while Shiki and the MC watch.
Eventually they join in and the MC remains involved for the rest of the chapter.
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Rating: 4
Ji Yoo and Park A-Seon have lesbian sex with each other before the MC joins them for a threesome.