Itsuka Aeru Kimi ni (Series)

At Okagi Castle, Yuuki informs his childhood friend An that his family is moving away. Vowing to return when he is older, Yuuki confesses that he would like them to go out when that happens. Unsure if their feelings for each other will remain the same when they next meet, Ann runs off in a panic, only to encounter a portal at the entryway of the castle. Stepping through it, she finds herself 50 years in the future. In her confusion, An is approached by a boy named Kibou and his friendly robot, Butler-kun. As luck would have it, Kibou's grandmother instructed him to lend a hand to any troubled girls he encounters at the park, so he offers to be her chaperone. As the three explore the city, An notices that despite how much Okagi has changed, the old charm never evaporated from the nostalgic townscape. [Written by MAL Rewrite]