School Lain and Wired Lain Are Not Just Online vs. Offline Personas
SPOILER!
It is tempting to explain the early split as a shy girl acting bolder online.
The series keeps making that explanation too small. Lain sometimes lacks memories of what the other Lain has done. Other people encounter versions of her she cannot account for. By Layer 07, the personality shift can happen in the same room under direct pressure.
What changed
The question moves from 'why does Lain act differently online?' to 'what counts as the same Lain when memory, behavior and other people's perceptions disagree?'
Why it matters
Identity in this series is social as well as internal. The Lain other people know can become powerful even when the Lain at school does not remember creating her.
Debut: Ep 002 - Girls
Other People's Memories Become Part of Lain's Identity
SPOILER!
Layer 08 makes the idea literal.
A rumor about Alice is tied to an aggressive Lain that the ordinary Lain rejects. Lain discovers that she can remove the information, but the repair reaches further than deleting a file. People's memories change with it.
What changed
Lain is no longer merely discovering that other people carry different versions of her. She can now alter the memories that make those versions socially real.
Why it matters
Once memory is editable, identity stops belonging only to the person being remembered.
Debut: Ep 008 - Rumors
Mika Shows What the Wired Looks Like to Someone Who Never Chose It
SPOILER!
Mika begins the series as one of the most ordinary people in the Iwakura house.
That is exactly why the messages telling her to fulfill the prophecy are so disturbing. Mika has not pursued the Wired, installed experimental hardware or asked to be part of anyone's theory. The intrusion simply reaches her.
How you can tell
Her scenes do not give her the investigative control Lain increasingly has. Mika receives the strange event rather than entering it.
Why it matters
The series needs someone who proves the Wired is not only dangerous to people who go looking for it.
Debut: Ep 005 - Distortion
The Iwakura Family Feels Normal Until Normality Becomes a Job
SPOILER!
The Iwakura household is emotionally strange long before the plot confirms that something is wrong with it.
Yasuo is warmer with computers than with most people. Miho reacts to increasingly impossible events with almost no visible surprise. Mika is the family member who most obviously behaves like an ordinary sister.
Layer 10 turns the discomfort into information when Lain's family life effectively ends and the people occupying those roles leave them behind.
Why it matters
The show does not reveal a happy normal family and then destroy it. It lets you slowly realize that the normality itself may have been part of the structure surrounding Lain.
Debut: Ep 001 - Weird