The Brilliant Healer’s New Life in the Shadows

Isshun de Chiryou Shiteita noni Yakudatazu to Tsuihou Sareta Tensai Chiyushi, Yami Healer to shite Tanoshiku Ikiru
一瞬で治療していたのに役立たずと追放された天才治癒師、闇ヒーラーとして楽しく生きる

Source

The Brilliant Healer's New Life in the Shadows
Isshun de Chiryou Shiteita no ni Yakutatazu to Tsuihou Sareta Tensai Chiyushi, Yami Healer Toshite Tanoshiku Ikiru· 一瞬で治療していたのに役立たずと追放された天才治癒師、闇ヒーラーとして楽しく生きる
novel

Life hasn't been kind to Zenos. He was born in the slums, and his dirt-poor background has denied him almost every opportunity. After an encounter with a healer, he throws himself into studying to become one and finally catches a break when an adventurer invites Zenos into his party. Zenos is thrilled—so thrilled, in fact, that he's willing to put up with his teammates treating him like garbage. They fail to appreciate his talents and ultimately kick him to the curb, claiming he's outlived his usefulness to them. Now bereft of money and out of options, Zenos decides to put his self-taught skills to use elsewhere and opens an underground clinic. Word quickly spreads about the brilliant healer working incredible magic in the city's shadowy underbelly. Even the royal palace is taking notice... Can Zenos buck the odds and carve out a life for himself in a world that's done nothing but spit in his face? And can he save the lives of the patients who wind up on his doorstep in the process? (Source: J-Novel Club)

Alternative

The Brilliant Healer’s New Life in the Shadows (MangaToon)
Isshun de Chiryou shiteita no ni Yakudatazu to Tsuihousareta Tensai Chiyushi, Yami Healer to shite Tanoshiku Ikiru Cresfall Sennyu-hen· 一瞬で治療していたのに役立たずと追放された天才治癒師、闇ヒーラーとして楽しく生きる
manga

Born a poor man in the slums, Zenos never had opportunities in life, so he decides to forge his own opportunities by teaching himself the curative arts after a chance encounter with a healer. When an adventuring party led by a man named Aston extends him an invitation, Zenos is elated—only to then be treated like dirt by his teammates. Despite Zenos’s diligent efforts to hone his skills to nothing short of perfection, the party deems him useless and kicks him out. Bereft of money and options, Zenos starts an illegal clinic and becomes a shadow healer. Word of his healing genius spreads quickly throughout the city’s underbelly, and as his reputation grows among the dregs of society, knowledge of Zenos’s esteem reaches the wrong ears.