RYUU TO AYUMU NARIAGARI BOUKENSHA-DOU: YOUZUMI TO SHITE S-RANK PARTY KARA TSUIHOU SARETA KAIFUKU MAJUTSUSHI, SUTERARETA SAKI DE SAIKYOU NO SHINRYUU WO FUKKATSU SASETESHIMAU

Dion, a healer, was thrown into the deepest part of a dungeon in a plot by his fellow party member. As he was facing certain death, he found a wounded dragon there. Dion healed the dragon with the last of his strength, and it turned out that it's a divine dragon named Eldora. Now that Eldora has regained her power, she will join Dion the exiled healer on a journey together as adventurers. Meanwhile, Yuki, the leader of the party that ditched Dion, was searching for him alone....... (Source: Bunkasha, translated) — Description from AniList community (anilist.co).