Ashikaga Yoshiaki appears in the anime Nobunaga Concerto as the fifteenth shogun of the Muromachi shogunate, taking the position following the death of his elder brother, Yoshiteru. Physically, he is depicted as an adult male with gray eyes and short black hair that reaches approximately ear-length. His character is defined by a deep-seated pride in his lineage and the authority that comes with the title of shogun. He carries a strong sense of entitlement, believing firmly in the power and prestige of the Ashikaga name. However, this proud exterior consistently gives way to a pronounced cowardice that emerges when he is placed under direct threat or pressure.

Initially, Yoshiaki secures his position in the capital city by forming a strategic alliance with Oda Nobunaga, who provides the military force necessary to install him as shogun. This relationship is the central axis of his role in the story, but it quickly deteriorates as Yoshiaki becomes resentful of Nobunaga's growing power and influence. Rather than a grateful ally, he views Nobunaga's strength as an insult to his own authority, and this resentment fuels his primary motivation: to check Nobunaga's rise and preserve the traditional power of the shogunate. To this end, he works politically against his former benefactor, demonstrating a talent for conspiracy and alliance-building despite his personal flaws. He actively forms a coalition of Nobunaga's enemies, including the Ikkō sect leader Hongan-ji Kennyo, as well as the Azai, Asakura, and the warrior monks of Mount Hiei. Yoshiaki gives his active support to Kennyo's declaration of Nobunaga as an enemy, which helps to ignite the larger Ikkō-ikki uprising.

Despite his political scheming, Yoshiaki's inherent weakness becomes his undoing. During the decisive confrontation at Makishima, his innate cowardice cripples his ability to act effectively, and he contributes to the coalition's setbacks through his ineffectual leadership under duress. He attempts to flee rather than fight but is captured and brought before Nobunaga. Instead of executing him, Nobunaga chooses to banish Yoshiaki from Kyoto, a calculated move to avoid the political consequences of killing a sitting shogun. This banishment strips him of all political relevance and serves as the final blow to the Ashikaga shogunate's authority within the narrative, solidifying the shift in power toward Nobunaga's campaign for unification. His development arc is therefore a downward one, moving from a newly installed leader with potential to a resentful conspirator, and finally to a powerless exile whose personal failings of pride and cowardice lead directly to his downfall. His primary abilities are political manipulation and forming strategic alliances, yet these are consistently undermined by his inability to perform under pressure, making him a tragic figure whose ambitions far exceed his personal fortitude.