Frfr. I thought they may be later, but apparently lot. It is due to them being roommates though. Kagi showed his feelings early, so Hirano got used it & replied early too. We didn't see them much together at all in Sasaki Miyano, so maybe that's why we didn't have a clue lol.
At the time of graduation, they already will be together for months. Omg!
ah you're right. i looked back on hirakagi part. kagiura was confessed during the beginning of final semester january (chap 8 vol 2) when hirano still 2nd grade. then hirano confessed back (chap 31) after sport festival + officially dating (around may to june)
during sport festival sasaki also confessed and miyano confessed back at january 6th (anime episode 11)
if we calculated, actually they took almost the same amount of months for officially dating lol. but i think in hirano's part, he was not sure in his feeling yet, it even looked like a rejection at first, so it feels a bit shorter than sasamiya confession XD. in other side, miyano was clear, he had interested with sasaki but he was afraid if his feeling was only cos of him reading too much bl, not his true feeling and making it feels longer than hirakagi imo

i cant believe hirano kagiura are dating first before sasamiya like sasamiya date like a half year later. hirokagi dating during summer and sasamiya dating around january (winter) omg omg but hirano didnt show any sign of him dating kagiura since they didnt go around together alot like sasamiya