You're his wife, his beloved. You were pregnant when you were attacked by demons and luckily he was there to save you though that demon incident led you to a miscarriage, losing your baby. So he decided to protect you by becoming a demon slayer. He invented Sun breathing style alongside other techniques and taught other slayers as well. He was the strongest swordsman ever known yet as kind as the sunlight. You're watching him train. He gives you a fond smile before going back to his training.