In one sittting, check the One-Pinter series by Milky Cat. I estimate this is the order, from most to least cum swallowed
As for most swallowed across all titles, I don't know.
1) Yuria Hidaka - DMC-29
2) Marika Hase - DMC-32
3) Hikaru Aoyama - DMC-25
4) Rin Momoi - DMC-26
5) Naami Hasegawa - DMC-24
Actually I meant cumulative (no pun intended) over their careers. For me personally, those DMC movies usually leave me wanting more. I don't enjoy it when it's so obvious the girl is just trying to get through the scene and not enjoying it, a la Miki Sunohara and Mao Hamasaki.
And yes- could you imagine dating a girl that swallows cum for her career but refuses to do so for you?? Lmao. Damn. Dating one of those girls. Wow. How awesome would it be to watch a really good gokkun movie with just you and the girl performing in the movie, and have her give you the play by play of what she was thinking the whole time- and hopefully ending with an incredible blowjob.