I'm not sure exactly what Mang BT21 is. It could be a fan-made manga based on BT21, or a special edition or spin-off of an existing BT21-related comic.
Well, BT21 was developed by a group of creative minds associated with a specific brand or organization. The process likely involved a lot of collaboration and ideation to come up with the unique characters and concepts.
Sorry, I don't know who created Mang BT21. You could try looking through manga-related social media groups or blogs, someone there might have the answer you're looking for.
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.
The bt21 original story is about a group of adorable characters. They were created through the collaboration of BTS and LINE FRIENDS. These characters embark on various adventures in their own little world. Their stories often involve themes of friendship, self - discovery, and having fun together. They each have their quirks that make them lovable.