Miho Iwakura 岩倉 美穂 (Iwakura Miho)
Lain's mother says almost nothing and looks at her daughters with a flat, unreadable face. She cooks, eats rice and sits at the table, and her rare lines are curt. Where Yasuo at least pretends to be interested in Lain, Miho does not even pretend, which makes the house feel colder than any of the Wired scenes. The Japanese Wikipedia character notes describe the couple's relationship as unexpectedly good despite her not understanding his hobby. Ueda's original concept, as he told FRUiTS in 1998, started with Lain's mother and the question of why Lain was born, but that strand was dropped in the TV version, leaving Miho as a near-silent presence. Rei Igarashi voices her. The game has its own version of Lain's mother with a more ordinary home life.
More (spoilers)
Miho, like Yasuo, is not Lain's real mother. In Layer 10 she disappears with the rest of the family, leaving an abandoned house with an open fridge and dead plants. Ueda described the family at Otakon 2000 as watchers sent to gather information. After Lain's reset, Miho is back at the breakfast table as if nothing happened, teasing Mika about her diet.
Sources: en.wikipedia.org archived · ja.wikipedia.org archived · animenewsnetwork.com archived · lawmune.net · lawmune.net · lain.wiki