Tomoki Sakurai, a teenage boy, strives for a peaceful and quiet life, a core motivation reflected in his personal motto. Since childhood, recurring dreams of an angelic figure in a field awaken him in tears, adding emotional depth to his character. Orphaned at ten when his parents departed to travel, he was raised by his grandfather. This upbringing ingrained a perverted worldview through constant exposure to lewd philosophies, manifesting in Tomoki's daily sexual harassment, peeping habits, and objectification of women. Yet he maintains unexpected boundaries—refusing to peep on girls using toilets and never targeting Ikaros, an inconsistency he cannot explain.

Childhood isolation followed an incident where his adventurousness caused friends' injuries during a bird-nest expedition, leading parents to forbid associations. This loneliness ended when Sohara became his neighbor and closest friend. He taught her karate and orange cultivation, forging an enduring bond while remaining oblivious to her romantic feelings. His life transforms upon encountering Ikaros, a winged Angeloid who falls from the sky, imprinting him as her master. He develops deep affection for her, navigating complex relationships with Angeloids like Nymph, Astraea, and Hiyori Kazane in a "love pentagon." Despite lamenting their disruption of his tranquility, he treats them as family, rejecting their servitude to encourage freedom, independent choices, and human-like emotions.

In *Eternal My Master*, Tomoki breaks his bond with Ikaros, misinterpreting her emotional detachment as a chain to sever. This backfires—Ikaros experiences profound distress, interpreting it as abandonment. Her tearful plea for reinstatement forces Tomoki to recognize her genuine love and dependence. He restores the imprinting chain, acknowledging her feelings and his role as her anchor. Their reconciliation faces a test when Ikaros carries him toward Synapse; her body disintegrates due to a security mechanism, culminating in a kiss, her first smile, and a declaration of love before she vanishes.

Tomoki exhibits surprising resilience, enduring extreme trauma like Sohara's "karate chops of doom," energy blasts, and planetary weaponry—often with comedic groin invulnerability. He displays leadership, such as orchestrating snowball battle strategies, and wields "Thunder Wang," generating defensive and offensive lightning from his genitals. In the spin-off *Yūryō Bukken Mō Dame Sō: Furo, Toilet to Tenshi wa Kyōdō Desu*, 26-year-old Tomoki appears unemployed, financially supporting Yurara Tategami by purchasing cosplay outfits like bunny suits and nurse uniforms via social media.

His character embodies contradictions: a lecherous "Butt-Monkey" yet a compassionate "All-Loving Hero" capable of profound sacrifice. His journey reflects growth from selfishness to self-awareness, particularly in understanding love and responsibility toward those depending on him.