A 7 year age gap shouldn't be too weird. If I'm not mistaken, Kainer was 20 years old when he has stabbed by his sister, when Saye was only 13 years old. Now she's 18, Kainer is 25. That's the same age gap as my parents and is totally not weird. Add to that this was in the "olden days", then the gap is totally fine and not creepy at all.
That being said, the way Kainer said it was totally weird and creepy lol, why did he have to say it like he was an old man who fell in love with a 13 year old lmao. He was basically just a young man during that time, and literally just ended his teen years.
The ways he took care of both the bitch and the father were so satisfying that he didn't have to behead them, he already murdered them by words. Bitch acted like her tongue got cut off and can't even whine or argue, while dad's objections were drowned by the torrential downpour of blades ala Jon Snow-style.