He was a guest at Sumi Jo's 'La Fantasia' concert on the 14th and 15th, singing "Person, Love" with her. Sumi Jo introduced Yoseob with a lovely poem, showing her affection for Yoseob, and said, "His depth makes people touched. I hope Yoseob's song is loved by many people."

He also sang "Mother", the song that prompted Sumi Jo to invite Yoseob to her concert. She saw his video on YouTube and was so touched that she asked him to stand on stage with her. 

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Yoseob himself was incredibly happy, writing on his Instagram, "Sumi Jo.. I'm so thankful that you allowed me to stand on this incredible stage.. And I'm so thankful to the people who decorated my uncool voice with an amazing accompaniment. It was a great experience, and I learned so much. Thank you. Also, thank you to everyone who came. Thank you!"