The following contains spoilers for Episode 16 of Komi Can't Communicate, "It's Just a Merry Christmas," now streaming on Netflix.
Ren Yamai has been obsessed with Shoko Komi since Episode 4 of Komi Can't Communicate. Although she thinks of herself as being "in love" with Komi, it's quite obvious to everyone else that she doesn't respect personal boundaries, let alone Komi as a person. When she's not threatening the people in Komi's life, she's either competing with them for her affection or finding new ways to manipulate people and situations to her favor.
In Season 2 of Komi Can't Communicate, Yamai finds herself lusting more strongly after Komi than previously established, and she's started sinking to new lows to satisfy her sexual urges. This was most evident in Episode 14 where she obsessively thought about looking up Komi's skirt and kept devising ways of manipulating her into showing her underwear. Episode 16 of Komi Can't Communicate continues on this trajectory, with Yamai's behavior starting to border on sexual harassment.
It's Christmas Eve in the Episode 16 story "It's Just a Merry Christmas," and Komi's birthday falls on Christmas Day. While Komi is out holiday shopping with her brother Shosuke, Tadano and Najimi are out with their group of friends buying birthday gifts for her. The only friend not shopping with the group is Yamai, who is already at the mall ahead of everyone's schedule. Although at first, it seems Yamai found out Komi's birthday through Tadano or Najimi, she confirms while shopping that she actually used her own network to find out Komi's birthday and had already been thinking about what to get her for a present for months.
This is, of course, not surprising coming from Yamai, as it's consistent with her yandere behavior, but at the same time, it goes to show just how dangerous her behavior really is. While it's been long-established that Yamai does not respect personal boundaries and has been known to stalk Komi to her house, the recent revelation that she has a "network" through which she learns Komi's personal information means that she's not done finding new ways to violate Komi's privacy. The revelation further hints at what Yamai intends to do with Komi, which most notably comes through when she arrives at Komi's house.
Prior to entering her house, Yamai is already thinking about giving herself to Komi as a birthday present and follows that up with the thought of "getting inside Komi." This leaves nothing to the imagination other than a very disturbing image of sexual assault taking place, and Yamai doesn't intend to keep that thought to herself. Once inside Komi's living room, Yamai orchestrates a seating arrangement to ensure she will be the one sitting next to Komi at the kotatsu table. What she doesn't count on is Komi choosing to sit next to Tadano regardless of the seating arrangement, which leaves Yamai feeling terribly cross.
Her determination to "get close" to Komi forces Yamai to come up with another "creative" way to get Komi to do as she wants, and she settles on doing a non-alcoholic version of a popular Japanese drinking game called Ōsama Game (King Game). Per the rules of the game, the number of chopsticks matches the number of people in the room and are numbered as such, minus one. The remaining chopstick is labeled the "king" chopstick. To play the game, the numbers and king label are concealed, and each person draws a chopstick. Whoever gets the king chopstick calls out a random number and dares the person holding that number to perform an embarrassing action.
Yamai intends to use the game as a way of "daring" Komi into doing something sexual, but luckily for Komi, Yamai manages to stop herself from taking things too far. While it can be easily interpreted that Yamai restrained herself out of recognition that she was about to exploit Komi in a disgraceful manner, it's far more likely she did so out of the realization she and Komi weren't the only people in the room. Had Yamai decided to play King Game alone with Komi inside the latter's bedroom, there's a good chance that Yamai would've run wild with her "dares," resulting in sexual harassment.
On the whole, it's becoming increasingly clear that Yamai's behavior is edging closer and closer to future sexual harassment, which could result in the loss of a friend on Komi's list. While Komi herself might be devastated to lose a friend at first, at the same time, it's a friend she can do without. As the saying goes, "There are plenty more fish in the sea," and a toxic friend like Yamai can easily be replaced with someone better.