Each clique in the game has a single gay male member in which you can gift flowers too, as well as kiss. You can gift certain male students with flowers, so if you have already completed Art 5 then you can still unlock this trophy, it is just somewhat harder as there are less boys in which you can gift flowers too. I highly advise working on this trophy as early in the game as possible, especially before you complete class Art 5, as completing this class skips the ability to gift a girl, and allows you to kiss her straight away, as such you will find it difficult to gift certain individuals with flowers. Once you have picked a total of 50 flowers the trophy will unlock. Once you exhaust all flowers in your inventory, return to the flower bed and pick some more and repeat the process of gifting them to girls around the school. I suggest you kiss the girl once you have gifted her with flowers, as this will help towards unlocking the Casanova trophy. You can then run away from the girl and come back a little later to gift her some more flowers.

In order to gift a flower to a girl, hold to lock onto a girl and then keep pressing until the bunch of flowers options appears (see below screenshot). You can only gift flowers to girls that like you which are the older senior girls, you cannot gift flowers to younger girls. In order to gift flowers you must have completed Art 1 class, which is the third class available to you in the game, as this will reward you with the ability to gift presents in exchange for kisses. You can hold a maximum of 10 flowers in your inventory at once, and the only way to get rid of flowers is to gift them to either girls or boys. In order to pick flowers walk up towards them and press. The easiest location to find them is out the front of the Girls Dormitory and the Library (see below screenshot).

Flowers can be found in specific flower beds throughout the game.

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