"Contact experiment" (接触実験, sesshoku jikken) is an ambiguous term used in the show to describe certain experimental procedures conducted between between a human and a Seed or Seed-derived entity. Three are known to have been performed: The first, about which little is known, was conducted between a human and Adam, playing a role in the initiation of Second Impact. This was eventually followed by two other contact experiments, of an apparently different nature, involved in the early development of the Evangelions.
Adam & Second Impact
The Katsuragi Expedition Team undertook a mysterious procedure on September 13, 2000, which one scientist referred to as "the contact experiment with the donor". This "contact" was apparently physical, and somehow resulted in DNA "diving" into Adam and "physically fusing" (to use their own cryptic phrasing). It has been forwarded as the direct impetus for Second Impact. It is also very strongly intimated (in the manga, essentially stated) that Tabris was born from this joining of Lilin genes and Adam's body. The identity of the donor is unknown.
Yui Ikari & Eva-01
In 2004, Yui Ikari participated in a contact experiment with Evangelion Unit-01 at her own request. In what appeared to an accident to onlookers, but was in fact planned by her, Yui's body dissolved into LCL and her soul was absorbed into the Eva's core. The subsequent attempt to salvage her soul back into a reconstructed body failed due to Yui's desire to remain in the Eva.
Kyoko Zeppelin Soryu and Eva-02
At an unspecified date, Kyoko Zeppelin Soryu undertook a contact experiment with Evangelion Unit-02. Unlike Yui's experiment, Kyoko's does not cause her soul to be completely absorbed into Eva-02. Rather, only an aspect of her soul resides in Eva-02 - the part that loves her daughter above all else. However, due to her soul being split, Kyoko goes insane and later commits suicide, leaving Asuka without a mother. During Episode 25', both the insane and maternal aspects of Kyoko are heard talking to Asuka at the same time, suggesting that the remainder of Kyoko's soul was salvaged into Eva-02 at some point after her suicide.
- Even with the scarcity of information on the first contact experiment, it seems to be inherently different from the two that followed.
- In ADV's Platinum translation of Episode 21', a Katsuragi Team member's line is furnished as, "The DNA that was inserted into Adam is already physically fused!" This is misleading, however: The Japanese clearly says that the DNA "dived" (daibu shita). However, since the concept of DNA "diving" of its own accord makes no apparent sense, ADV's Shoko Ono may have attempted to reinterpret the line into something that did.