The answer is: "OST song" refers to the song in the OST. OST referred to the original music in movies, TV series, and other film and television works, and the song part was the OST song. According to the search results, some OSTs of movies and television works included some songs, such as the theme song of the TV series OST of " A Thought of Passing Mountains," many of Zhou Shen's OST songs, and Yu Kewei's Top Ten Classic OSTs. Therefore, an OST song referred to the song part of the original music in a film or television work.
The OST lineup for the second season of Celebrating Years had already been announced. Among them, Li Jian sang the theme song " In My Lifetime," Zhou Shen sang the ending song " Excuse me," Liang Long, Liu Duanduan, Zhang Haowei, and Guo Zifan performed the promotional song " Aiya." These songs would bring more musical elements to the second season of " Celebrating Years," adding more emotions and atmosphere to the plot.
A common theme is friendship. Dororo and Hyakkimaru's bond is often explored further in fanfics. Another theme is redemption. Since many of the characters in the original have complex pasts, fanfics may delve into how they seek redemption for their actions.
The Dororo manga has a rather complex and bittersweet ending. Dororo and Hyakkimaru's fates are intertwined in a way that leaves a lasting impression on readers.