So, Jun prefers his girlfriend to call him just "Jun". Big thanks to
astraldrop2012 who told me that Mao called Jun "Jun" in the AnS. I thought it was "Jun-kun", but after astraldrop2012 pointed it out, I could clearly hear "Jun, Jun. I feel sick" (I also carefully listened to it in slow motion and it was clearer that she whispered "Jun, Jun..." kkyyyaaaa~). @ second: 00:00:10, dozo.
Edit
chocochipcooki heard "chotto" rather than "Jun, Jun". Mina, please listen carefully and let me know. I still heard "Jun, Jun" (maybe my delusional mind only wants to hear "Jun" haha).
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sub credit: stormy_team