Rika and Kristy's maternal grandmother, Seiko Hata is rather open-minded and serves as a balancing element between her daughter and grand-daughter, with mixed results. Rika's grandmother tries early on in the show to relate to Rika, but Rika refuses to let her.
Later, Rika's grandmother discovers Renamon's existence and dubs her Rika's "guardian angel". She seems not at all surprised that Rika is a tamer, and promises Rika that she will keep her departure to the Digital World secret from Rika's mother. Rika is shocked that her grandmother is so understanding, and from then on is kinder and more open about her feelings to her grandmother.
In Dimensions, Seiko begins to play an even larger role in the tamer's life. She tries to encourage the girl to speak to her mother before leaving for the Digital World to recover Renamon. Later on, she serves as a supportive listener to human and digimon characters alike.
The most interesting development for Seiko thus far would be her gaining the title as the eldest tamer when she became partners with DarkBiyomon after the death of Chiyo Suzume. This partnership is still in the early stages.