You can develop relationships or bonds with the NPCs found in different areas in Postknight by giving out gifts to them. And in exchange, you will receive gift boxes from them. A gift can be given every 4 hours while a natural decay of bonds occur if you do not visit or give a gift to an NPC for a certain period.
Every NPC likes different types of gifts, gifting them an item they do not like will drop the level of bond significantly. There is some hint for you in the game but some of you may not notice it. Therefore, here is a list about the gifts items they like for you.
List of NPCs and gift items they like (credits to Postknight wiki):
Magnolia: Found in Pompon Village after finishing Timber Path V. Likes Honey, Mushroom Soup, White Lily, Polka Dot Ribbon and Sweet Delight (Event).
Fleur: Found in Pompon Village after finishing Creek Trail V. Likes Apple Juice, Curry Rice, Green Orchid, Leaf Handkerchief, Honey and Spring Bloom (Event).
Dahlia: Found in Shello Bay or Caldemount after ranking up to PostKnight Rank B. Likes Hoop Earrings, Roast Beef, Beer, Red Rose and Classic Desire (Event).
Senna: Found in Griffondell. Likes Milk, Grilled Salmon, Feather Pendant, Yellow Daffodil and Summer Charm (Event).
Camellia: Found in Caldemount. Likes Salad, Coffee, Peach Tea, Pink Carnation and Blushing Allure (Event).
Asteria: Found in Valley of Gold. Likes Pancakes, Coffee, Lavender and Bright Devotion (Event).
Noticed the little smiley face besides the item? It is a hint for you in game!
You can obtain gifts from chests, buying from the Merchants or drops from enemies. Noted that some items can only be bought from merchant in certain area. Have fun building up bonds with the girls!