*8.5. Application of the System*

The ability to talk with elderly people is becoming increasingly important for social robots because dialogues play an important role in building human–robot relationships. Social robots instruct elderly people to take medicines, exercise, undergo cognitive training, and suggest lifestyle improvements in order to sustain physical and mental wellbeing. Instructions in such situations may not work well if the relationship with elderly people—in other words, a sense of trust, security, and familiarity—is not built. Conversely, if the relationship between elderly people and social robots is well formed, the instruction will be more effective. Therefore, not only robots as companions but also a various other robots will need to have a certain level of dialogue with humans. The proposed twin-robot dialogue system would be useful from the viewpoint that they can sustain dialogues up to 12 min 51 s.

**Author Contributions:** Conceptualization, H.I. and Y.I.; methodology, Y.Y. and T.I.; software, M.C., T.A., and T.I.; validation, Y.Y. and T.A.; formal analysis, T.I. and M.C.; investigation, T.I., Y.Y., and M.C.; resources, Y.Y. and T.A.; data curation, T.I. and M.C.; writing—original draft preparation, T.I.; writing—review and editing, T.I., Y.Y., and T.A.; visualization, T.I.; supervision, H.I. and Y.I.; project administration, H.I. and Y.I.; funding acquisition, H.I. and Y.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by NTT DOCOMO, INC., JST, PRESTO Grant Number JPMJPR1851, JST, ERATO Grant JPMJER1401 and JSPS KAKENHI Grant Number 19H05691.

**Acknowledgments:** We appreciate participants and caregivers who had participated in the field trial, and the facility manager that had admitted us to do the field trial.

**Conflicts of Interest:** Mariko Chiba, Taichi Asami and Yoshinori Isoda are working at NTT DOCOMO, INC., which is one of the funders of this study.
