>>2695849being gay or not implies sexual desire, either physical or psychological. lain, as the meta-dimensional, trans-data being it portrays, has trascended that mere biological mechanism.
all decisions have already been taken by her, as she commands all bits of information in the Wired, hence the universe. she can be gay and not gay at the same time, if she wants.
back to the series, i dont think their relationship is romantic. nonetheless, lain is shown somewhat awkward and shy, making it difficult to read her feelings/emotions (if there is any, as explained before).
