I'm assuming the question is about 'To You, The Immortal' by Yoshitoki Ōima, sometimes stylized as 'To Your Eternity'. It's a fascinating story that follows an immortal being created as a spherical orb. This entity, later called Fushi, starts with no form, thoughts, or senses, but it gains them by 'taking' the form of things that stimulate it profoundly, beginning with a rock and then a moss-covered wolf. The core plot is Fushi's journey of learning what it means to be human, to live, to love, and to suffer, all while outliving everyone he comes to care for.
It's structured in long arcs, each centered on a new human companion Fushi meets. He first mimics the form of the wolf that belonged to a lone boy waiting in a snowy wasteland, which sets the tragic and beautiful tone. Each arc ends with the death of those companions—old age, violence, illness—forcing Fushi to grapple with endless grief and loneliness. The antagonist, the Nokkers, are mysterious beings that seem intent on destroying him, adding an existential threat to his philosophical journey. The plot is less about a traditional 'goal' and more about the cumulative weight of experiences shaping an immortal consciousness.
I found the early arcs, particularly with March and Parona, to be the most emotionally devastating. The series constantly asks what 'morals' or purpose can exist for a being that cannot die, making the title 'To You, The Immortal' feel like a direct, painful address from Fushi to the reader. It's a slow, often heartbreaking chronicle of accumulation—of forms, of memories, of losses. The manga's pacing allows this feeling of vast, lonely time to really sink in, which is its greatest strength, even if it makes for a tough read at times.