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.
Well, one of the main themes is the relationship between the normal and the abnormal. The novel uses the presence of supernatural elements to highlight how the characters deal with things that are out of the ordinary. It's about how they adapt and change in the face of these strange phenomena.
Araragi Koyomi is one of the main characters. He is a high school student who has had an encounter with a vampire, which gives him some unusual abilities. Senjougahara Hitagi is also a main character, known for her complex personality.
I'm not sure about the popularity of this specific visual novel. There are a lot of visual novels out there, and while 'bakemonogatari' as a series has a following, the 'netorare' aspect might be a more niche or polarizing factor that could affect its overall popularity.
It's mainly about various supernatural and strange stories. The characters often encounter and deal with different apparitions and odd phenomena. It has complex character relationships and deep, often philosophical, dialogues.