Ah, young anon. You have come to the right page. ItoGo is quite a glorious pairing indeed.
ItoGo is meme shorthand for the pairing of Itoshikinozomu and Yuuago. The alternate name for this pairing is ItoYuu, and is just as commonly used.
They have wonderful chemistry, with Ito professing his love in various ways (such as suggesting he'll break into Yuuago's house and sleep in his bed), and as Yuu tries to keep up his tsundere front (because if yaoi has taught you anything, it's that they only say no because they want it).
This pairing has also spawned genswitch art of the two.
Fused nipples, huff huff~