It's probably another ntr bait and not a real love rival. The author makes those ntr baits about like every 2 chapters that it became so predictable.
Kanan's sister probably asked her to seduce him or something.
I also don't understand why it's tagged as pornographic. I once reported that it's wrong, but it was refused, so maybe they fuck in the later chapters or something.
In most countries the age of consent is 16 so idk what's the fuss. You say like it's strange and bad and stuff, but even in most states in the USA it's 16.