On the first day, Arrive at Osaka directly. Take the train to Namba station and checkin in Henn Na hotel, rooms are a bit small, but they have everything you need and the dinosaur staff is super fun :)
Depending on the time you arrive, you can visit :
Shitenno-ji temple
Shinsekai market for sunset with the famous photo spot of the Tsutenkaku Tower
Abeno Harukas just after sunset for the best views of Osaka
Dotonburi for some super street food and shopping
Hozenji Yokocho / Ukiyo Koji, for some photo of small alleys