What Shan't Be Seen ( 見てはいけないもの / みてはいけないもの / mite wa ikenai mono / Something You Must Not Look At ) is the forty-third chapter of the Elfen Lied manga series.
A weary Arakawa arrives at the island home of the Diclonius Research Institute, greeted by Shirakawa, frustrated by her brutal treatment after informing Chief Kakuzawa about the death of Professor Kakuzawa. She is shocked at being taken nearly two kilometers underground into a hot area, which Shirakawa describes as 'the origin of the new humanity,' or "Project Lebensborn." She is shown to be carrying a small crate like a pet's travel compartment and is completely overwhelmed.
In the Maple House, Yuka tasks a reluctant Kouta with house cleaning in preparation for her friend's arrival, shooting back at his snarky rejoinders, and warning him against doing 'anything strange.' Sent out to fetch sweets to have with tea, he passes by a pretty young girl on the stairs out, wondering if this is her friend. An awkward moment ensues when her skirt flies up in the wind, revealing a bladder diaper, and leaving him confused and the girl completely, shocked and embarrassed.
At the Institute, Arakawa enters a secret part of the facility, an underground pond with high air pressure and a large bed of raised stones protruding inches from the ground. Standing in the midst of this is Chief Kakuzawa, who names the place for a mythical island inhabited by demons. She prepares to hand the crate to him, which is revealed to hold his son's head when he asks whether or not she saw his son's horns. An attempt to offer her condolences abruptly ends when he declares her to have seen too much and shot an incredulous Arakawa.
- Though in the chapter she is not yet named, this chapter introduces the newest and final addition to the cast of main characters: Nozomi.
- Yuka is on the chapter's cover, wearing a slightly less conservative outfit than her standard attire, capped off by high-heeled boots that go up to her shins.