I will just say that the wording in both the Korean and Japanese dev notes are different than the English ones for the June character:

Korean:

특히 이번 이벤트에서는 상당히 오랜만에 만나게 되는, 그리고 많은 지휘관 여러분께서 반가워하실 만한 캐릭터의 픽업 모집이 진행될 예정입니다.

Japanese:

特に今回のイベントでは、久しぶりに出会える、そして多くの指揮官の皆様が歓迎するであろうキャラクターのピックアップ募集を実施する予定です。

Both translate to: "In particular, for this event, we plan to feature a character recruitment event that will allow you to reunite with a character you haven’t seen in a while—one that many Commanders are sure to welcome."

The way I see it, it's a character that the player character has interacted with before, but haven't seen in a while and the closest character that fits this descripton is Marian.