Ai-chan's video upon reaching 300,000 subscribers ends with her thanking her viewers in English. It's really sweet.
Her response video to PewDiePie's reaction to her cover of his video cover of "Hej Hej Monika". Not only is Ai-chan happy that someone such as Felix noticed her work and loved it, but she proceeds to read out a thank-you message to him in English. Said video was then watched by Felix (who was touched by her emotionally), completing the cycle.
Pretty much anytime Ai-chan finally clears something difficult could fall under here, especially in a horror game. Her joyous "YATTA!" after finally beating the Botanic Panic stage of Cuphead, for example.