Single-minded devotion to one thing; wholehearted, earnest, or determined—focused on one person or purpose.
彼は仕事一途で、休みの日もほとんど休まない。
He is single-minded about his work and hardly takes days off.
彼女は恋に一途で、相手のことをずっと思っている。
She is devoted in love and keeps thinking about her partner.
成功を夢見て、一途に努力を続けた。
Dreaming of success, (he/she) continued to work single-mindedly.