The protagonist (you), admires his senior at work, Asami Senda. She's his mentor at work and the ace of the company. A woman gifted with both beauty and brains plus a pleasant personality, she is sought after by many business partners looking to negotiate contracts.

After the company drinking party, such a high caliber woman suddenly invites him to an after-party with just the two of them. They miss the last trains of the day and the two of them stay at a hotel; Naturally, there's no way they'll just go to sleep without doing anything...

This is a book compiling the "Shokuba no Senpai" series posted on Twitter.
This includes a newly illustrated story with a total of 33 pages: it's Episode #01 fully depicted in R-18 form.
(Source: Melonbooks)

Contains 10 stories combined into one book:

1. Would You Like Another Drink? / Mou Ichido Nominaosanai? (もう一度飲みなおさない？)
2. Senpai And Today's Second "Good Morning" / Senpai to Honjitsu Nidome no Ohayou (先輩と本日2度目のおはよう)
3. Opposite Effect / Gyaku Kouka (逆効果)
4. After Drinking at Senpai's Place / Senpai no Uchi de Nonda Ato (先輩のうちで飲んだあと)
5. Senpai And Business Trip / Senpai to Shucchou (先輩と出張)
6. Senpai Wants To Go to The Ocean / Senpai wa Umi ni Ikitai (先輩は海に行きたい)
7. Senpai And The Ocean / Senpai to Umi (先輩と海)
8. Senpai And The First Time... / Senpai to Hajimete... (先輩と初めて…)
9. Senpai Didn't Have The Luxury To That Time / Senpai mo Ano Toki Yoyuu Nakatta (先輩もあのとき余裕なかった)
10. Beginning to End of the First Night / Hajimete no Yoru no Ichibushijuu (～初めての夜の一部始終～) Newly-drawn exclusive (R18)

Stories #1-9 are Twitter shorts, story #10 is a 33-page new illustration and chronologically a full R-18 depiction of story #1.

Note:
Live-action JAV adaptation: URE-095