Nidome no Isekai, Shounen datta Kare wa Toshiue Kishi ni Nari Dekiai shitekuru

"The boy I saved before becomes an older and a highly talented knight!" One day, Sara is transported to another world and saves a boy named Luke who was pursued and collapsed in the forest for some reason, and decided to live together with him. However, just as Luke is beginning to recover from his injuries, Sara is abruptly sent back to her own world. Three years later, Sarah returns to another world again and is reunited with 25-year-old Luke, the finest ice magician in the country and a knight who earned baronetcy for his achievements! He used to be 10 years younger than she, but now he's two years older and is now a romantic interest. "I'll reward you with my entire life," he says as he began to dote on Sara.

(Source: Kadokawa, translated)