Due to the influence of the global pandemic, online and distance learning has replaced traditional classroom and face-to-face interaction so students can continue learning. Internet mediated self-directed learning also climbed to a new height and foreign language learning from YouTube video is a very popular learning method for many. Furthermore, YouTube videos can supplement cross-cultural knowledge for foreign language (FL) learners, which is a critical yet hard to develop ability for FL teachers. However, unlike for FL textbooks, the cross-cultural elements have not been examined thoroughly for YouTube videos. Therefore, this study analyzed the most subscribed and watched Japanese Chinese-as-FL YouTuber, “Lee Sisters ch”, which is also the official representative of HSK (Hanyu Shuiping Kaoshi) test. We selected 30 most watched videos and analyzed their contents according to Chastain’s Big ‘C’ small ‘c’ culture framework. The result showed 86.67% of the most popular 30 videos covered topics about culture: 23.33% of the videos were related to big ‘C’ culture and 63.33% were about small ‘c’ culture. Similar to earlier researches on FL textbooks, “Literature” was the main theme of big ‘C’. On the other hand, “Everyday living” was the most frequent small ‘c’ topic, which is a unique phenomenon for YouTube FL channels. Furthermore, not only did the portion of big ‘C’ and small ‘c’ cultures match the suggestions of FL scholars, the language used in all videos were also mainly in Japanese that fit the needs of Japanese CFL learners. It is concluded YouTube video may be suitable to learn cross-cultural knowledge for FL learner, especially for Japanese students.