| title | ISBN-13 (ISBN-10) | year of publication |
|---|---|---|
| Hajimete no hito to demo sumuzu ni hanaseru shitsumonryoku: Chinmoku de kimazukunaranai 53 no pointo | 978-4-7696-1014-4 (4-7696-1014-9) | 2009 |
| Step 5 fan your question marketing will increase to 1000 people ISBN: 4046539100 | 978-4-04-653910-6 (4-04-653910-0) | 2013 |