The Hydrangea-Colored Picture Letter is the 28th overall episode of Tegami Bachi
Lag ponders over what to write in the letter bullet for Gauche, and confesses to Sylvette that he doesn't have much experience writing letters. Lag's job takes him to a mansion in the countryside where he delivers a letter to Rei Attlee.
He is welcomed by a exceptionally tall maid, Kimidori. Rei wants Lag to find out who sent her picture letters of hydrangea-colored mountains, and explains that the pictures remind her of her childhood while living in a village. Rei's parents received governmental positions in Akatsuki and had her moved to a location close by to receive care as she is sickly.
However, she is cheered up by the letters, which she feels they tell her to keep on fighting her illness. Lag searches through town for information on the origin of the letters and finds out that the hydrangea colors came from Hydrangea dyes (this episode calls them Blue Romeo flowers). While searching for Niche at the mansion's garden, Lag finds Kimidori picking Blue Romeo flowers and concludes she is the sender, which she readily admits.
Kimidori is glad that Rei is encouraged by her letters, but refuses to tell Lag further and makes him promise not to reveal this. However, when Lag wonders how to tell Rei, he discovers Colbasso has claimed credit for the letters for her own selfish reasons. Although Lag promised not to tell, he shoots a shindan into the letter, which reveals a flashback of Rei's childhood.
It turns out that Rei met and befriended Kimidori when she was young. Before she moved, Rei gave her a matching hairpin as proof of their friendship. When Kimidori grew older, her family owed debts and she was forced to sell the hairpin. Feeling guilty for having sold the hairpin, Kimidori leaves home to search for Rei's current residence and eventually finds it. She then plants the Blue Romeo in the garden to remind Rei of her childhood. Rei reunites with Kimidori and thanks her for the happy memories. Inspired, Lag decides to draw a picture for his letter to Gauche but was disappointed as his drawings are awful.