Naruto: Wooing Tsunade from Day One!

(Naruto + Single Heroine Tsunade + Romance + Action) A failed author transmigrates into the Naruto world, becoming the younger brother of Konoha’s White Fang, Sakumo Hatake, and the uncle of Kakashi. He gains a cheat ability—enhanced cellular activity. Coincidentally, just before the Second Shinobi War, he participates in a Jonin meeting where he supports Tsunade's proposal ahead of Dan Kato, marking his first encounter with her. From then on, he launches an intense pursuit, winning her heart during the war. Tsunade: “Kawakaze, why do I keep losing to you?” Kawakaze Hatake: “Because I’d like to live a few more years...” Kakashi: “My uncle is amazing, I’m his biggest fan!” Kawakaze Hatake: “Keep it low-key, keep it low-key.” — Description from novelcodex.org