Wow, 25 days and you already got 17 5-star units?!! How did you get so many in such a short time? Lucky with gacha much?
Oh btw, keep your 4-star units. You're gonna need them for the World Defense missions, with Winter Rose being the hardest to assemble a squad. In fact, you can clear events up to Ultimate using just 4-star units (evolved, max lv and max affection), if the gacha gives you a lot of BS.